The biggest advantage of disposable cameras is the cost. This opens up possibilities that would normally not be considered for us to take photographs.
We often leave behind that expensive digital camera except on specific occasions when we deliberately go out to take pictures. But every day in our lives we can have opportunities that seem to arise that we say, “If only I had my camera with me”. The cost of damage or losing a disposable camera is small (except for those photographs you just took).
Having a camera in your car glove compartment is a great location for a camera after all we are quite often in our car but not always with a camera. Pop one in your sports bag, ok occasionally it might get squashed but do not let that you miss an opportunity. In your Golf bag for when you get that hole in one or break your handicap is a celebration you would not want to miss.
Keep one in your office desk for that memory of somebody`s last day at work or promotion. For accidents than might happen a visual record is often much better than memory.
Actually the list could be endless for situations that arise. The only factor you need to remember is to keep a camera close at hand and get used to the idea of taking pictures. It might take a while and you might forget you have one. After a while the idea will take hold and you wont pause to take that picture for whatever reason.
This is probably the best aspect of disposable cameras.
With waterproof disposable cameras the use is somewhat more limited and specific. But these are equally as useful. Water Water Water everywhere and not a camera in sight. Well no more, the fear of electronic equipment and water mixing can be gone. Like having a camera in your sports bag, you can have a waterproof camera too. Swimming, canoeing, kayaking, sailing whatever your water sport or even as an spectator you can take those photographs too.
Disposable and waterproof are great reminders that you can still take that pictures while having fun. Some may be damaged or lost in your particular activity but remember it didn't cost you much in the first place.