You're making some assumptions here which are not necessarily true:
- ALL drug tourists are all a bunch bundled up in a cheap room and only eat from grocery stores
- every "drug tourist" comes for the sole purpose of drugs; nothing else
- all "families" (as you put them) stay in more expensive hotels and spend more money
- "families" and drug tourists are mutually exclusive (everything is either black or white)

I think you are wrong in all those assumptions. I know quite a few "serious, responsible adults" (for the lack of a better term) who have visited Amsterdam not for the drugs as a primary purpose but who have indulged, being in Amsterdam. For at least one group trip that I know of (a group of some 12 friends went last year) Amsterdam got the edge because of the added option of mj. They spent plenty of money on museums, restaurants and the like and only smoked once.

I know people who would never touch mj and who stayed in a cheap hotel when visiting Amsterdam. (They don't really care about the hotel since they're there to be tourists and be out doing stuff as much as possible and really spend a minimum amount of time actually in the hotel room.)

A small business owner providing relatively cheap services (e.g. a 2 star hotel) may not be happy with his business going bust. Even if ALL the patrons were drug tourists (which can't be true), they still help some people earn a living.

You never see people getting high and getting into fights, becoming violent and causing mayhem. While that is true for alcohol, that's never a problem with stoners. They're relatively easy to deal with and their money is good for the local economy.