It seems to be the "make up" of these type of shows though doesn't it, ....like on "Wheeler Dealers" with Mike Brewer and Ed China; one total bell*nd and one decent bloke, one guy goes shopping and the other guy does the hard mechanics.
I think it's so if you don't like one of the onscreen guys you'll definitely like the other and if you don't like either then you'll still watch for the awesome cars they do.
Your right it does seem to be the formula that these kind of shows use but I'd much prefer to see a more serious approach. I sometimes cringe and feel embarrassed for Tim when he's in full tit acting mode.