>At the last conference I attended, ~9/10 engineers were running macbooks

They're both tired tropes. There is a pretty reasonable mix of hardware and software run by 'engineers' and no where near 90% are macs.

edit: https://www.statwing.com/demos/dev-survey#workspaces/2496

That site has some pretty good statistics related to OS usage among programmers and some hardware usage, like iPod/iPhone, which I think is a decent indicator of whether or not these people own macs.