Why does being profitable justify being even more profitable by paying fewer taxes?

It’s not about encouraging profitability (that only one proof of a real company) as much as allow businesses to grow, without people faking businesses to write off personal expenses. Properly reporting expenses can allow new or growing businesses to reinvest in themselves. I agree that there should be a different structure for large business but I’ll give a hypothetical to outline why it’s important for small businesses.

Let’s say a new family owned machineshop does $200k in sales in its second year. Pre-tax after all other expenses the business has netted $50k. Post tax (-$40k) they’ve got $10k left to reinvest. They want to buy $20k worth of machinery to grow the business. If they can deduct $20k for the machinery from the $40k in taxes the can buy it. If not they can’t.

Meanwhile the large international conglomerate machineshop down the road makes $400k a year post tax. If the want $20k in new machines they just buy them. This isn’t because they run a better business w/ better margins or product but because they have more volume.