I squat in Olympic shoes and not for flexibility issues. I use them because they prevent lateral movement of my foot. When you're walking out heavy weights, it is added security that you're not feeling your foot rolling at all. It's like they add width and weight to your feet. I would say, more often than not, I see people wearing them in competition; IPF walked out squat competition. You may see them less in a monolift because of the different set up.
I love my shoes for bench as well. If you want to keep your feet flat on the floor, having a bit of a heel lets you pull your legs further under you.
If it's a money issue, I'd get the belt first though.
Oh yeah. bla, bla, bla more meat in the freezer.