Smell is subjective, some people dislike fragrance, some love fragrance. Fragrances are included in detergents to cover the smell of surfactants, which smell unpleasant. Sensitive, plant-based or eco detergents still contain fragrance (as well as fewer or weaker surfactants), just less than the mainstream versions.
The safety of detergents and ingredient regulation is undertaken by AICS (The Australian Inventory of Chemical Substances), which is administered by NICNAS (National Industrial Chemicals Notification and Assessment Scheme).
Labelling requirements are mandated by Australian Consumer Law (ACL) Schedule 2 of the Competition and Consumer Act 2010, and Commerce (Trade Descriptions) Act 1905, and Commerce (Imports) Regulations 1940 for ‘Country of Origin’. 
Ingredients are listed on packaging in descending order by either mass or volume for those that are greater than 1% using the INCI (International Nomenclature of Cosmetic Ingredients) name. Any that are 1% or less can be listed in any order. Australian labelling requirements do not mandate that fragrance raw materials are listed in the ingredient listing of a product or on an MSDS; the only statement that must be listed is the term fragrance or parfum. (Trade Practices (Consumer Product Information Standards) (Cosmetics) Regulations 1991) 
The maximum allowed concentration of a fragrances in a final personal care product is 1%. In general, this is also the amount used in laundry detergents, although this is not mandated. (Australian Regulatory Guidelines for Complementary Medicines Part IV: General Guidance) 
Proprietary ingredients are confidential formulations; they include fragrances. Fragrances are classified as low risk, often with a long history of use, and are generally used in small quantities in finished products in this regard. This is a reason why individual raw materials used to create fragrances are not listed on packaging.
Many products claim to contain ‘natural’ fragrances, in most cases this is a marketing claim as natural fragrances and synthetic ones are composed of the same raw materials, there is no requirement to state otherwise.
The definition of a ‘naturally occurring chemical’ is very specific and is legislated under Industrial Chemicals (Notification and Assessment) Act 1989 (ICNA Act).
Most chemicals derived from nature require some type of processing before they can be used in a cosmetic product. The following requires assessment and consideration:
Does the process involve deriving or extracting it and
Has there been a change in the chemical composition during the extractive process?
If the chemical is classified as ‘naturally occurring’ the term ‘contains naturally occurring’ can be used.
What is a ‘naturally occurring chemical’?
It is defined as an unprocessed chemical occurring in a natural environment or
A chemical occurring in a natural environment, being a substance that is extracted by; manual, mechanical, or gravitation means, or dissolution in water, or flotation, or a process of heating for the sole purpose of removing uncombined water, without a chemical change in the substance.
Many products contain chemicals derived from natural sources such as plants and minerals. These cosmetics are often marketed as ‘natural’, ‘organic’ or ‘pure’. Not all chemicals from natural sources meet the definition of a ‘naturally-occurring chemical’ in the Industrial Chemicals (Notification and Assessment) Act 1989 (ICNA Act).
In recognition that many consumers want to know what is in the products they use, the fragrance industry has published the list of over 3000 fragrance ingredients from which fragrances are formulated, and which are used in consumer products worldwide. All ingredients on this list have passed the International Fragrance Association (IFRA) safety standards and are used in consumer goods worldwide.
This initiative provides consumer information whilst protecting proprietary details of specific fragrance formulae, which take considerable time and financial investment to develop.
This complements Accord’s ‘What’s in it?’ initiative, whereby companies voluntarily disclose ingredients in their cleaning products, air care products, automotive care products, polishes and floor maintenance products.
All fragrance ingredients on the IFRA list have been evaluated for safety. These ingredients have been concluded to present “no unreasonable risk to human health and the environment, and to be safe under their intended conditions of use”.
The Research Institute for Fragrance Materials (RIFM) is the international scientific authority for the safe use of fragrance materials. RIFM’s Expert Panel, an independent and international group of dermatologists, pathologists, environmental scientists and toxicologists, evaluates scientific fragrance data to make sure that there is no risk for the consumer or environment as the ingredient is currently used. Evaluation of fragrance ingredients takes into consideration possible effects on the skin, including skin irritation and sensitisation, the effect of sunlight on the ingredient, and toxicity to body systems.
According to the IFRA Code of Practice, “Safety data for all fragrance ingredients that are commercially available and offered for sale as such must be submitted by the ingredient manufacturer to RIFM for inclusion in the Fragrance Ingredient Database.”
When warranted by the data, the RIFM Panel instructs IFRA to issue a Standard either restricting or banning a fragrance material. To date, 174 substances have been banned or restricted.
Every year, a random compliance audit is undertaken on fragranced products. In 2012, 50 randomly-selected products from 10 countries were tested for compliance with the IFRA Code of Conduct. These products spanned different categories including perfumes, cosmetics, personal care products and household products.
The independent auditing body found 100% compliance with the IFRA Code. 
For more information on what is in detergents and the function of the raw materials see the Mainstream Detergents, Enzymes, Optical Brighteners, Plant based, Sensitive & ‘Eco’ Detergents pages and The Wash Wise Detergent Ingredients Info Sheet.