It is widely held, by the more "seasoned" members here (read "old"!

), that BIR curries today taste and smell considerably different than those of yesteryear (e.g. those of the 1970s and 1980s). It is one of the reasons, I feel, that members are probably chasing different end points in their curry cooking endeavors.
Why is this? No doubt the reasons are many and varied.
These are some of my thoughts (albeit largely conjecture on my part):
1. Change in Ethnicity of BIR Ownership:a. Up until 1998, around 85% of all BIRs were owned and operated by Bangladeshis (formerly Eastern Pakistan)
b. This percentage had declined to around 65% by 2003 (and has no doubt declined further since)
c. The percentage of Bangladeshi owned restaurants continues to decline in London and the further north of England you go
d. In Glasgow, there is now a predominance of Punjabi owned BIRs
(Reference: Wikipedia http://en.wikipedia.org/wiki/Curry)It is reasonable to assume, therefore, that today's BIRs reflect this increasing ethnic diversity of restaurant ownership in more diverse BIR menus (i.e. regionally Indian based rather than Bangladeshi based), ingredients and cooking techniques.
2. Market Differentiation:To me, there seems little doubt that many BIRs are trying to differentiate themselves, from the traditional high street BIR, by moving more "up market". More exotic menus are presented, usually emphasizing the use of fresher and more exotic ingredients and generally based on regional Indian curry cooking (e.g. Punjabi, Peshawar, Nepalese, Sri Lankan, Goan, etc). This will often go, hand in hand, with more traditional Indian cooking methods (e.g. perhaps not using a curry base).
The resultant curries will not only be different (that is not to say worse) from those typical of yesteryear, but will also generally cost more and take longer to prepare and serve.
3. Changes in Food Regulations:There can be little doubt that food hygiene standards have become more stringent over the years. I suspect that restaurant practices, which were once commonplace, are probably no longer so commonplace. This might, conceivably, include things like the declining use of "reclaimed oil" (for example)
4. Health Awareness:There is also little doubt, in my mind, that Indian (and Chinese) restaurants once used copious amounts of MSG as a flavour enhancer. There is also little doubt, in my mind, that they also once used copious amounts of salt, artificial food colouring and lots of "unhealthy" cooking oils and fats.
It seems to me that the trend, nowadays, due to public awareness and subsequent pressure, is for BIRs to try and reduce the quantities of these "unhealthy" ingredients in their curries. In fact, many BIRs now advertise the reduction in their use of these ingredients as a market differentiator and selling point. However, there is also no doubt, to my mind, that some of these ingredients are fundamental to developing the taste and smell of curries from yesteryear.
So, modern day curries may arguably be a little less unhealthy for you, but perhaps at a penalty (to some people's minds) of a different (some might say inferior) taste and smell.
5. Availability of Commercially Prepared Ingredients:To me, it is apparent that, nowadays, BIRs make more use of pre-prepared commercial ingredients (e.g. curry pastes, curry powders, garlic and ginger pastes, processed meats, etc). Indeed, commercially available ingredients, such as Patak curry paste (use of which is now evident in most BIRs) would simply have been unavailable, for their use, prior to the early 1990s.
Once again, use of these pre-prepared commercially available ingredients no doubt results in a different tasting and smelling curry than those of yesteryear.
Well, these are my thoughts on why curries today taste and smell different from those of yesteryear. Has anyone any other possible reasons they would like to suggest?