I can't speak for other types of business, or any big business with 50+ employees for that matter. But for my small business, if I need another employee, I hire one. And if I do not need another employee, I do not hire one.
Taxes and expenses are NEVER the slightest consideration.
I do not hire someone just to have them around, because I like them, or in advance of having a need for them. Either I need more people or I do not.
I've never understood the argument about taxes and such vs hiring.
The same happens in the reverse too... If my taxes are cut I will simply have more money, but I am not going to hire an additional employee just to sit around and talk to me. Either I have work for them or I don't. And If I do have work for them, they will be making me money regardless of what my taxes and expenses are, because my competitors will have those same expenses.
I will not argue that it is this way for all business. But it certainly is for mine.