Maybe Apple, Facebook, and Google think they can develop their talent in house from their programmers?
To whatever extent they have trouble attracting researchers it's because you will never be able to publish anything or talk about your work in a finance firm. Academia is status/reputation/ego driven (not that there's anything wrong with this).
My friends in quant finance made more than 200k guaranteed their first years (not including performance bonus), and they did not have graduate degrees. It went up to more than half a million in a few years (including bonus).
The ramp up and ceiling is much higher in finance. First year salary for someone with a bachelors in a finance company may be comparable to someone with a masters/PhD in a tech company, sure.
The common complaint is that regardless of performance, their pay increases and bonuses end up being shit YOY and that the only way to make serious money is to hop from company to company every year.
One friend who builds trading infrastructure has increased his pay from $180k to north of $480k just by doing this and is about to go to his 5th or 6th fund (in roughly as many years). He kills it, ends up getting the token bonus they give tech people, waits out his non-compete and leaves.
They treat tech talent as commodity just as much as anywhere else. The other downsides being you usually can't trade your own account while employed.
Said friend would prefer to start a fund soon rather than keep this up as he'd rather be able to trade.
http://ijcai-16.org/index.php/welcome/view/sponsors
And at ICML
http://icml.cc/2016/?page_id=63
Have been to Google booths at IJCAI and got selected for interviewing based on my interaction at the booths.
Publishing isn't the focus of hedge funds so they don't get a lot of love.
It makes sense that academics would be interested in working for a company that will still allow the academic to publish.