i run et30 9.5 on the rear of the s15 and with a decent tyre (not stretched to buggery) i have to run about 3degrees negative camber to tuck the tops in. you can go lower in offset and stretch the tyre or run silly amounts of camber but the next thing though is to start hacking the hell out of the quarters or bolting bits of fibreglass over the top so you can fit wider wheels. and whats the benefit?
handling...no
grip...no noticeable
looks...can look good, but can ruin a nice motor as well
rubbing issues...probably lots unless more work is done
expense...yep, lots of this too if you want to do a proper job, roll and pull - oops paint split, repaint or fit overfenders? either way £££
lots of people want to use thier cars and make them look as aggressive as possible without compromising on any or all of the above things. at the end of the day, when you stump up the cash for a wide set of low offset wheels (and you do actually care about your car) then you are committing yourself to doing a lot of work to make it all work well and look tidy. some are happy to go at it with a scaffold pole and hammer which is all well and good, but the wheel firms will always cater for the majority which is the 10j and under, positive offset crowd......