Problem with an elected second chamber is that the only people who would stand would be yet more bloody politicians. And they would be the ones who've failed to get elected to the Commons. So, in time, it would fill up with not just politicians, but failed politicians into the bargain.
At least at the moment there are some people in there, NOT the hereditary peers, who've actually been successful at something other than climbing the greasy pole. I'm on about businessmen and women, successful writers, artists, sportspeople and the like.