Really? That has to be the most "sexy" job out of all of them. Anyone, and I do mean that, can build an app that runs off of 1-4 boxes and a single DB instance. Not many people can build a system that scales to 100+ boxes and a DB that spans several boxes (not counting slaves.)
By that time, you're having to solve the "hard" problems. That's where a back-end guy shines.
Please don't confuse what I'm saying. I don't know what type of developers that they are chasing but what happens after the startup phase and into the profitability/scaling phase is code cleanup. I've done enough of it to know that it's not that fun (or sexy, in my book) to see what shortcuts were made to get something working right now. Untangling that and getting it to work on a grand scheme doesn't sell all that well to the type-A 'let's hack this out!' startup mentality.
This is where you need the pragmatic developers who you probably wouldn't have hired at the start. They are (relatively) slow and tedious, but the job will be done right. This tends to be a natural flow of from start-up to mature company.
By that time, you're having to solve the "hard" problems. That's where a back-end guy shines.