It's all about cost and what users can accept. If a feature costs 10 times less, takes half the time to implement and is easier to maintain but produces the same result for the end user, why would software companies bother to optimise (if the end user does not care)?
Also, it seems to me that the optimisation on the web is done on speed at the detriment of memory usage.
Also, it seems to me that the optimisation on the web is done on speed at the detriment of memory usage.