To the OP, I shore dive quite a bit in Florida, and use a snorkel for that. It can be a long swim (1/4 to 3/4 mile) out to the desired reef. Obviously, I don't want to use my breathing gas for that. I could swim on my back, but due to our clear water I like swimming flat and face down to see what is below. This also makes for easier swimming (more efficient trim), and also easier to follow my compass bearing to and from the reef. So, a snorkel is great. I use a roll-up type (XS Cargo) with a quick clip. When I get to the reef, I take it off, put it in my pocket, and do the dive. Does not interfere with my long hose that way. I can breathe my tank down to my reserve out on the reef, then surface, put on the snorkel, and back to shore. If a chop has blown up during the dive (that happens regularly), swimming on the back all the way to shore would be miserable, so the snorkel keeps things much easier and more pleasant (and safer too). So, for you, I think it is a good thing to have. if you don't dive long hose, you can just leave it on for the entire dive--even easier.
Don't know about lakes, but if there is a cool wreck in the middle of the lake, and the lake is large, and you want to swim out and drop down as opposed to using gas to get there, same principle.
On my boat dives, it is always in my pocket. If I surface in rough seas and have to wait for the boat, I clip off my reg, use the snorkel to keep breathing easy and no water gulping, and when the boat arrives I am immediately ready to climb the ladder. If, god forbid, I ever got left and had to swim to shore, or be in the water many hours, in a chop or rough seas, the snorkel would change from a nice convenience to essential survival gear.
So, one is always with me, even if it might not be on my mask all the time.