Quality of software is pretty much irrelevant for startups. The code is usually crap and gets thrown away over and over anyway. The real focus is on people.
If the code is crap, that might explain why it gets thrown away over and over. In my experience, if code is well-written, it should pretty much always be possible to update, revamp, pivot, etc. Rewriting from scratch (especially repeatedly!) is a waste of time that a startup can't afford.
Engineers for startups are paid poorly and almost always work on technically uninteresting problems. Where are you going to get people who can write good code? And again, why would you bother if the hard part of startups is everything except getting the code to work?
Reminds me of this Joel Spolsky essay: http://www.joelonsoftware.com/articles/fog0000000069.html
The focus being on people does not preclude writing good code.