What we have learned how to do is deal with the conditions we encounter. I've done over 2,000 dives here now in all sorts of conditions and never ... not once ... wished I had a snorkel.
Most will never NEED a snorkel. I carry one for two reasons. One, I am the first out of the boat and can snorkel without using my air until everyone finally gets off the bleepin boat. And two, for emergencies. What would you do if you were taken by a rip current, drift, or other current, out to sea, only to surface and find the boat is gone and you have to swim it? On your back you can't use your compass, with a snorkel you can use underwater navigation and make your way back to land.
I realize this scenario is ridiculous, but my point is you never know when you may NEED it and in those situations you'd be best to be prepared.
____________
Ben