It's long been observed that once earning reaches a certain absolute number, quality of life and other intangibles quickly overtake monetary compensation as the primary driving force. Basically its saying if my options were 60k/year and great quality of life vs. 120k/year and shitty quality of life, I'm much more likely to take the 120k than if the situation was 120k/year vs. 240k/year.

The problem is very real, banks wouldn't be responding to it otherwise.

Also helps that tech companies are "winning" the PR war against traditional banks. Being a banker used to be fucking cool, now its lame.

Edit: okay, that last line was confusing, so let me try to explain what I mean: Most bankers aren't married to finance, it's not like they have this amazing passion for excel financial models. They are attracted to being at the very top of the talent ladder, in a position that offers the most challenge and potential reward. Nowdays technology is seen as an equivalent option for a lot of kids entering school