Trust me Clobbersauras, you feel it quite well when a large hunk of metal doesn't slam forward with all of the might of the recoil spring. Even on automatic fire you can feel the bolt cycle (or not) with each round you fire, or on the last one. Or on any misfire.
And if you lost count of your rounds and don't have something like, say, a tracer as the fifth last round in your mag (I'm talking about the 30-rounders I'm issued, nothing that's legally available on the civvy streets in Canada, of course), the feel of the bolt not going forward will be enough to tell you it's time to change mags.
As for the re-cocking, whether with pistols or rifles, I'm a charging handle/slide type of guy. The bolt catch on the C7/AR15 platform, sometimes, just doesn't want to cooperate. And when you need to get that rifle firing again quickly, you don't want to fiddle with that bolt catch. The cocking handle does the same job, and it's a lot harder to miss it than it is to miss a wee little button on the side of your rifle.
With pistols, there are some (ie: CZ 75) on which I can't easily reach the slide release because I have pretty small hands. As such, to get back into action quickly, racking the slide is just as fast, and keeps my firing hand in a proper grip. And, of course, the slide is a lot easier to grab in a hurry than a small button. On older pistols (read: the Brownings the CF use), sometimes the slide lock just doesn't wanna budge and the only way to release it is by pulling the slide back.