There's a whole lot of assumptions in that statement, most of which are dubious.

The last time I had a valet park and retrieve my car, the whole bunch of them were running, not walking, to take the car from you and to retrieve it. I handed the valet my claim slip and some folded money when I got my car, and he was gone. I can't imagine one standing around long enough to give you his email/paypal account when there's a long line of impatient customers waiting for their cars.

Housekeeping staff: I am almost never see them, so how much time do you plan to spend waiting for one to show up when you're ready to check out? Leave the folded money on the dresser with a slip of paper that says "Thank You" and don't interrupt their work.

And if I was a hotel employee and you asked for my phone number, email or paypal account, I would slowly back away and call for the manager.