I mean come on, it isn't honestly going to taste much nicer. Seems more like a bit of a novetly at the detriment of an animal.
You've got to remember that this is a cultural norm to the Japanese. It might seem nasty to us, but to them setting out poison and traps for rats could be savage and inhumane, not to mention fox hunting (which still goes on even if banned) or keeping thousands of chickens in cages in barns.
I don't think there's any point in one culture pointing fingers at another and saying "that's unnecessarily cruel". I'm not saying what they're doing is alright, just that we're not exactly on the moral high ground here.