This might be a silly question but from a newbie...I would like to understand a little better. I just got my first dslr - a Nikon D5300 and just learning everything about it. Plus I am starting to aquire better glass instead of just the kit lens that came with it - but as far as purchasing another camera body....why do you do that? I see a lot of people here have various camera bodies...so just curious as to why.
In the professional world it is highly advisable to have a back-up body of the same or similar quality as your main body. Both in case of camera troubles or accidents on a shoot, as well as for the benefit of having two different lenses mounted at the same time so you never miss a shot due to changing lenses. It is often a good idea to have a comparable crop sensor body to accompany your full frame bodies for those times when a full frame just will not give you the "reach" you need to shoot a distant subject. There are other, lesser reasons to have a second or even a third body on a shoot, but a Pro would NEVER be foolish enough to go out on a paid shoot with only one camera body, or just a single lens either.