The bottom line: house is easy as hell to beatmatch. Anyone who has tried can tell you this. To throw down a good, INTERESTING, and original house set, however is not easy. (which is probably why there are a million boring-a*s house DJ's).
Hip hop is harder to beatmatch, and as a result, mediocre HH DJ's end up scratching or backspinning every-other mix. Good HH DJ's mix beats, loop intros, juggle, and scratch in a mix from time to time.
Personally, I don't agree with this statement:
"but I don't think [scratching over house]should be done... At house jams, the dj isn't the focus it's purely on the music... The dj should be ignored"
Why not put on somebody's mix-CD and fire the DJ?
Granted, it is all about the music, but why not entertain the crowd? Ever seen Donald Glaude? One of the most entertaining house DJ's out there, definitely not "ignored" on stage, and he scratches better than most HH DJ's. Don't take my word for it, though:
" I hail Donald to be one of the most entertaining DJs in America to watch live." DJ Dan
www.moonshine.com/moonshine/artists/bio.cfm?artist_ID=13
Just my opinion,
Peace