Already successful companies rarely can hand out 5% shares just like that, the existing shareholders probably won't have it. I'm fairly sure the OP is referring

Already successful companies rarely can hand out 5% shares just like that, the existing shareholders probably won't have it. I'm fairly sure the OP is referring to "5% of app profits" offers, i.e. shares in a yet non-existant enterprise. You'd effectively be acting as an angel investor in a company run by someone who won't actually do anything. (investing time rather than money)