If you want to sing for your own pleasure then I recommend the bathroom. If you're going to sing in the presence of other people, and especially if you expect them to listen, then surely you have a responsibility to them to try do it sufficiently well that they will want to listen. Otherwise its just plain rude.

It appears to me that whilst some singarounds are keen to encourage people to sing (which is entirely commendable) they don't want to take the responsibility to encourage them to improve, and provide them with an environment in which they don't need to, and perhaps don't even see the need to. I'm sure they and their audience would enjoy it even more if they could be encouraged to gain the skills and started to get real, rather than sympathy, applause.