> that makes a massive difference because you end up thrashing main memory when you could be spending those cycles getting work done.

That is true, however there is a huge domain of problems where that isn't much of a concern, while development time spent on it is a concern.

Then sacrificing a bit of performance over development speed can be quite worthwhile.

Of course not a high frequency trading platform and not an AAA+ Game, but a small Webservice just taking data from a ("slow") database, doing little transformation, and sending over network .... less of a problem