Or a process of curiosity and discovery, as that's fun too. What's wrong with working out stuff by yourself? Most of it is the art of the bleeding obvious.Some people prefer the course to the alternative of reinventing all the mistakes, some of which are dangerous.
DPVs; fun to play with and you soon get to know the pitfalls of powering up or down or getting it caught as you jump in. Drysuits; soon realise how much practice you need, especially ascents. Not much to them.
Diving can be annoyingly 'nannying' sometimes. Let people play and don't spoon feed them.