It's one of the areas where preparation is very helpful - checking before arrival that the name and room number are right, finding out the layout of the place, including where the lifts are (and whether they need a key) etc etc. For some places, its best to meet somewhere outside, or arrange a place to meet outside the bedrooms.
What hotels really don't like is sex workers cruising in their public spaces - the lobby or bar. A friend does it, and has to be careful and very very discreet. Even then, they have still been asked to leave a number of places.
But if hotels made an effort to stop people using their bedrooms for 'bed dates', whether commercial or not, most of them would go out of business. Ultimately, they need the income, so they don't care whether you're meeting up for business, socially or for... business
Oh yes - depending on just where you are, this is another good reason think carefully before showing your face on ads / websites. The size of a big city brings both anonymity and a large number of hotels to choose from. Somewhere smaller often doesn't.