I reckon the UK thing of skinning up with tobacco is cos up until fairly recently the vast majority of herb sold in the UK was resin, & you just can't make pure resin spliffs, you gotta have a base material in there to keep it burning, hence the tobacco. Now there's loads of bud around, but the baccy thing's stuck. I prefer tobacco in my joints, even though I put enough bud in to keep them going, I just like the mix. A lot of US folks like an after toke smoke, us UK folks just like the during toke smoke