well the reasons for going pro are:-

1) you get sharper as a performer - more depends on it
2) you get the best equipment - you can't afford not to
3) you are no longer in that back seat with Karl Malden - I coulda bin a contender. You find out whether you could or you couldn't. One of the great mysteries of your life solved.
4) you start paying attention to what works - rather than bullshit about is real folk music/art or whatever your hangup about music is
5) because of this last one, you get an insight into the lives and works of the great artists which is totally denied the civilians. You get to understand the calls they make, the basic shrewdness of most pro musicians.
6) at meetings of musicians (infrequent as it tends to be a solitary occupation) you have war stories to tell. stand amazed as the greats have even gorier tales than you have!


There are probably more, but its half past one a.m.