Trips to museums are my favorite, I love art and photography exhibits. When I visit New York for business I always schedule a cultural activity among my "extracurricular schedule" or shopping at few of the store we do not have here in Florida; even a trip to the Rockefeller Center for ice skating is a nice thing to do and not very pricey.  
Tons of things to do in the Northern States (Philly, Boston, NY). Touring can be stressful so why not mix it up with a bit of pleasure so you can generate revenue and see the world?. Some cities may not have a lot of attractions (specially in the Midwest) so I figure that will not leave us with much to do but, to stay in the room, read, do homework etc...specially under bad weather (rain, snow, cold weather).

Very rarely am I going to go blow the very funds that I left town to go make...seems a bit stupid, which is why some providers rent and lease, and others own everything they have. I've gotten spa treatments, tanned, etc. but never just went out and blew a few grand on shopping, knowing what I left at home that week. Point is, when I toured, I could not simply make that money up the next day or the next week, so what I made actually amounted to something. I used to always go to dinner off the clock for the company if I booked past 5 pm. Free meal, great company, getting to see the city through the eyes of a local...priceless.