Why should I hire the Doug White One MAN Band, and not hire a "real" band?

First of all, a really good band is very expensive.  And though it is not always true, most "weekend"  bands are pick-up bands.  They just throw together whoever happens to be available at the time.  Sometimes they're good, and sometimes they're bad.  I wouldn't trust my event to a part-time band.  I want a consistent product that I can count.  Don't you?

Can't I just find a student to play music for my wedding ceremony?

I wouldn't entrust one of the most important days of my life to a non-professional.  Unfortunately, professionals cost significantly more money than non-professionals.  Pay the price. Be happy with the product and sleep better, knowing that everything is going to be taken care of.  No worry's mate!