Cars are 4-strokes because weight is not an issue, emissions - and they can be abused and will hold up long term.
If someone is fouling plugs on their 2-stroke all the time - it is becuase they don't get it fixed. Either your jetting is screwed or your oil flow is screwed. If you take care of your two stroke, which does take more time and more of a hassle to many, so they don't, but if you do, they should last you just as long as a four stroke.
4-strokes require less maintenance, there is no doubt. This is also beneficial to the manufacturers because many of their warranty claims are paid out even though it was customer abuse, 4-strokes cut that # down significantly.