Because that growth is not sustainable in the majority of cases. Sure, there are exceptions, but I bet you're not going to be eagerly handing the org money back once growth flattens out.
In very rare cases do startups have that kind of growth and in many of them their unit costs are bad and they are making less and less money. In the few cases wherein sales are growing, AND they are more profitable, AND it wouldn't make more sense to put the money elsewhere - then yes - fat wage increases are possible, for a short period. In almost no companies is this reasonably sustainable.