Deducting losses or capital reinvestment from your taxes is in no way a subsidy or even a tax break at all. That is just accounting at it's most simple. You take the money coming in and subtract the expenses going out. Now yes obviously it gets more complicated because you can spread those losses out over time etc but it is still the same basic concept.Your questions runs the full gamut of business. From the little one man real estate office to a huge pharm operation. I would hate to rely on start ups for economic growth alone. The tax laws allow for recovery of capital for reinvestment promoting economic growth from all.
Sounds as though you would prefer a whole new Corp. tax system.
Here is an example that will really give you worms. Say your company has a customer that goes bankrupt. That company sticks you for $ 150k. The US gov't will reimburse your taxes going back 7 years. Why? The US Gov't considers Corp taxes a loan. My personal experience here is getting taxes back with a 70k loss in 1969 and a 95k loss in 1993. A corporation is also allowed the defer taxes with losses carrying forward. Those reimbursements allowed us to continue and start contributing back to the economy. My company is just one small example, I would bet it is one of tens of thousands.
And no I am not saying we should rely on startups alone for growth. Clearly most of the growth will come from existing buisnesses. But the fact is without new buisnesses our economy would not survive.