While I agree with the rest of your post, I don't think they (the airlines) are asking for trouble. They get money that they would not get with more rational MCTs. The OP is an excellent example (if my guess about the flight #s is correct). UA could not sell an IST-EWR-LAS combo with a more reasonable MCT unless it included an overnight connection or an additional connection in Germany (via the LH revenue sharing agreement). If UA did either, some other airline would get the money.

If the connection dosn't work because of WX or ATC, then what does that cost UA? I assume it's very little. As for driving away repeat customers with bad connections, well... repeat customers would probably know better (or at least, like dand99, have the good sense to ask question the connection).