Profit is the net result of investing capital. Revenues don’t matter.

If your startup turns a profit but still wants or needs to reinvest those profits in hiring more or more equipment, they still have to pay taxes on those earnings and only can reinvest half of them (there are some provisions to shield some reinvested profits from being taxed, but they are limited).

I’m all for taxing dividends and capital gains when investors cash out, I’m just saying don’t do it on profits that are reinvested.