> empirically, removing the exemption discourages R&D.
Not clearing a road means fewer people use it, but you not going out with a shovel to clear a public roads isn’t you discouraging their use nor is you canceling your plans to clear said roads.
It didn’t create a level playing field, it just discouraged a very specific type of R&D while ignoring all others. All other types of employee salaries follow certain rules and some can optionally follow R&D rules. Software is now the only one required to follow 5 year R&D amortization so the deck is now stacked against software.
The default situation is whatever was yesterday. I’d be astonished to learn that even a single significant civilization functioned without subsidies or patronage of priorities held by a society’s leaders.