Costs money (which may or may not be reimbursed) and time. Providing an ironing board and iron are cheap and, while doubtless less common than it used to be, is probably something some number of people expect. (I've never personally used them in a hotel.)
Hotel laundry services of any kind are unbelievably expensive in my experience. Usually US$10-30 per item, or the local equivalent, with e.g. socks and underwear being at the low end, slacks and collared shirts at the high end. Dry cleaning, of course, is a significant premium beyond that.
I thought it was just a US thing when I was younger, but I've found it to be true even in other countries.
Yeah if the hotel is nice enough then usually you can have suits and shirts pressed for a fee. If they don’t have on-site “wash-and-fold” then they probably won’t press clothes either.