I would be willing to bet that while many of the "4 star" hotels have public jacuzzi's, they don't have rooms with jacuzzi's in them. Also, many of those that do have such rooms the tubs are too small for more than 1 person, and they may be in the bathroom rather than the bedroom. At least that's been my experience.
I've yet to find a website that allows you to search for in-room jacuzzi's. You generally have to find the hotel, and then search all the available rates to find what types of rooms are available. Ideally, you want to see a picture of the room to confirm that you're getting a two person tub, and it isn't in the bathroom. I know a few hotels have red heart shaped tubs, which may not really be what you want unless you're taking your SO there.