Tire question

This may have been discussed before. I understand the theory behind reversing a rear tire to mount it on the front. My question is what is the advantage of using a rear tire on the front. Could it be the different tread design which would put more rubber in contact with the road and therefore better grip. I'm just curious on the reason for doing this.

Also, has anyone thought about putting a rear MC tire on the rear of a trike instead of a car tire. I would think that a 180 or 200 would fit. The down side that I see is that you would only wear in the center of the tire and not so much on the sides because you won't be leaning like you would on a 2 wheeler. Being retired I have nothing better to do than sit around and think up crap like this. :D

the big advantage of the rear on the front is there is normally for rubber depth (thicker) tread on a rear than on a front tire. So it SHOULD last longer because more tread to wear off.