^Yes, if the bride and groom aren't registered, I'm sure some guests are lost. So, some people just register out of social obligation, not because they are looking for a handout. Remember, even extremely wealthy people who don't need anything still register when they are getting married (or for a first baby.)
I agree that the "wishing well" is asking for a handout and really shouldn't be used except in the case of a very young couple who really are just starting out.
If I ever get remarried, I'd be tempted to register only for sporting goods and gardening supplies. Oh, and my other half sometimes moans that my unmatched and flimsy goodwill silverware is not up to snuff, so maybe just register for that. Is that tacky? Probably, but it would give people who insist on buying a gift some ideas.