[palata]

I would say: because nobody cares, "memory is cheap".

Same reason why software gets slower every time hardware gets faster, why everything expects a fast internet connection, or why it's impossible to buy a movie without DRMs (say if you want to have the file and add subtitles for your language):

Users don't care, they keep using/buying the non-optimized stuff. And devs are more productive (and companies make more money) by not optimizing anything.