Could someone help with cost estimate for TC and truck?

Why do people buy 4wd? (EDIT: I meant for TC use.)

I know what we use 4wd around here for -- mud. But on larger trucks, even a 1 ton dually, why would you buy 4wd? What is the benefit? Is it snow? Reason I ask is I can't see people mudding with a 1 ton carrying a TC. Sorry for more ignorance, lol.

As a sidenote, for just regular 4wd pickup use, around here, about 90% of them never see offroad, lol. Seems an unnecessary expense for most. Then again, we rarely have snow, they are just for mud around here.