I think it's a matter of preference for most and I've never checked the solder on the odd chain I've bought complete as it wasn't that important to me. I find that many of the bought ones don't have a jump ring but a fiddly end cap with a hole which is really difficult to put the clasp into therefore I always add a ring which I prefer to be of heavier weight and unsoldered but that's all I check.
Like Dennis says don't think we bother then doing the breaking point and hope that it isn't grabbed by a baby or snagged by a jumping dog both of which I've seen happen!