How are former casinos that re-opened as non-gambling hotels doing?

Claridge (reopened in May 2014)
Showboat (reopened July 2016)

and why would someone stay there instead of a hotel with a casino?

Might be more family friendly, or someone might have a gambling problem.
My friend used to attend two trade shows a year and stayed at non gaming condo hotel just south of Resorts. Never understood it, but that was his choice.

Not everyone gambles.

You have to look at all the qualities people want from a hotel, then what is different between them. It seems to me a casino hotel can be everything a plain hotel can be, but that might not be entirely true. My assumption would be a plain hotel, with similar real estate, would be quieter, more expensive, maybe cleaner, smaller, easier to get around. It's a good question I don't really know. I've wondered about it myself.

Claridge seems to be doing rather well thanks to its excellent central location.
Showboat I can't really say since it just recently opened.
IMHO Casinos during the week off season are a great value. One can often find a room Sun.-Thurs. for well under $100 and often 1/2 that.
During prime summer months the casinos can charge more and often lose the price advantage to non- casino hotels, some that where formerly casino hotels.
Weekends regardless of the season, casinos charge an arm and a leg for rooms. This is supply and demand economics exasperated by the casinos themselves.
Many casino rooms are comped on weekends. They often leave many rooms empty just in case a favored player needs it. So the supply has shrunk considerably yet the demand is high.
I would think that things will get worse with the 2,000+ rooms at the Taj now out of the A.C. market,