Good question. Being a liveaboard, I can answer this one pretty accurately.
The marinas have told me why. They get more
money by
renting slips to weekenders and people who don't come to the
boat often. Why? They don't need the extra staff and their facilities go unused 90% of the time, as do the boats tied up. A liveaboard needs to get mail usually, takes showers frequently, has needs of the marina from time to time, etc... All this costs money. The marina, in order to maximize profits (and attract the most wealthy clients they can screw with higher rates) does better without liveaboards.
Oddly, even with the cost of marinas in the
USA (I can see Manhattan from my
cockpit right now), it is about the
price to rent small studio or 1 bdrm apartment to both own the
boat and pay for the slip. That's how insane real estate has gotten here.
Of course, this assumes you like to live by the
water. If you live inland (not on a boat), you could rent a small 1 bedroom for a fraction of what it costs to
live aboard.
One thing you mention that I still find odd to this day is that actual hate for liveaboards some marinas have. I have run into this while calling to find one to
winter over at. I ran into a few that yelled at me and hung up on me at the point where they found I stay on the boat. Brewer's in Glen Cove, NY was the one that sticks out in my mind most. The odd part is that I kept an O'day 302 there for 4 years and gave them plenty of business. Now that I'm a liveaboard, they literally yelled at me and hung up in frustration.
It seems, based on the other post with the fire and theft in CT, that maybe all marinas should re-think and allow a certain small number of liveaboards so they can get free
security. Doing everything for maximum profit leads to a bad product/service. I don't think I have to reiterate all the horse crap I laid out about that already in other threads. ha ha