We turn ours on when we want hot water and otherwise leave it off.
The water heater is both small and not especially well insulated, so leaving it on all the time only burns up extra propane as that heat gets wasted sitting around waiting on somebody to call for hot water.
So we turn it on while fixing breakfast, and about the time we're done eating the tank is hot and we switch it off before starting to do the dishes. That way the heat we paid for gets used for those dishes, and only a tank full of cold water sits around until we turn it back on while fixing supper. We'll leave it on while doing the dishes, but then half-way through the last shower, somebody will turn it off again, so once more, only cold water sits overnight losing heat.
But I have no quarrel with anyone who wants to waste their own money leaving it on all the time because it's too much work to flip that switch 4 times a day.