Do you know why Ariane-5 exploded 39 seconds after take-off? It was because the inertial guidance system failed. And then the backup inertial guidance system failed. Then the rocket made a course correction it didn't need to, put the rocket in an aerodynamically dangerous position, and then the auto-destruct sequence was called, as designed in the case of significant malfunction, and worked perfectly.
Amongst the many lessons one could take away from the explosion is that having a backup system that works exactly the same way as the primary system means that if the primary system fails due to an inherent flaw (rather than failing due to an individual component malfunction), then the backup system will fail in exactly the same way. Indeed, that's exactly what happened in Ariane-5.
So, why the hell would we want to elect the Lords? We already have one elected chamber, and the people in it are, as previously mentioned, not necessarily the best people for making laws.
The Lords as is has its problems, but imagine if it had roughly the same composition as the Commons. Every law introduced by the Commons would get passed through the Lords on the nod, and vice versa. The Lords currently provides an important balance to the excesses of government because it is composed of members appointed by previous governments many years past. That is to say, the backup system uses a different algorithm to obtain its members.
I'm not claiming that the Lords as-is is a perfect or even near-optimal solution, but I'm damn sure that electing the Lords would make things worse, not better.