Proper application of caulking on a countertop
 

Hi everyone,
I recently got a job as a plumber.
I'm currently in training and one of older plumber was teaching me how to apply caulking today.
I saw him apply the caulking on the countertops edges and he didn't smoothed it at all afterward so I asked him why he didn't use his finger to do that (weted of course) and he told me that he, in fact all the other guys told me that, never smooths the joints even though there were some little bumps on it.
I was curious to find out to proper application of the caulking tonight and all the how-to I've read on the net so far say you have to smooth it somehow.
Is there a reason why you shouldn't smooth it, what's your take on that?
Thank you.