Nope, taxpayers do as much as is efficient. If a tax lawyer says "I can save you $50k in taxes by setting up a new corporate structure, but it will cost $25k to set up and another $10k per year to maintain", then the taxpayer probably won't do it.

But if rates go up, then it turns into saving $100k, but with the same costs of implementation and upkeep. Basically, as rates go up, it makes sense to do more tax planning.