Most scenarios we're taught we never need to use or have to use. Still a good exercise to go over it, know some different options, and if for some reason you ever do find yourself in one of these odd situations hopefully you react appropriately.
How many people have taken a CPR class? How many have actually ever been in a situation where they needed it? And how much of it do you actually remember if you took it once five years ago and never thought about it again?
Sure, tank position seems like a dumb topic, but people all around have bright up valid points. I've seen tanks slip out and have had to help them back in while underwater, and it's the reason I'll never dive a BC with only one tank strap. With two straps they can both be somewhat loose and your tank still won't go anywhere. The other side of that is the newest BCs have better tank straps then those of just 10 years ago and tanks are much less likely to fall out.
As for leaving, this is probably my first post in a year... I lurk more these days, if someone feels like they are getting burnt out then they should create some space. This place will still be here and still be the same whenever you are back into it.