For me it’s driving while under the influence. If you couldn’t tell, I like me some ganja. However I have long since held the belief that it is utterly insane to drive while under the influence of most substances, with maybe nicotine and caffeine being the exception. All too often I see other stoners smoking and driving, which I simply can’t fathom. I’ve only operated a vehicle once under the influence and it was just to move a U-Haul around the block to a different parking spot, which was such a scary experience while high that I refuse to even consider getting behind the wheel again while high.
Regarding backpacking: I experienced the ultralight community to be a very friendly and welcoming (although a bit nerdy) group of people. Yes, you CAN spend a lot of money on hightech equipment like many people do in cycling, archery etc. but it is also very common to MYOG (make your own gear). You can spend 200 bucks on the latest leightweight highend titanium cook pot. Or you can simply reuse an old fish can to cook in. And while this selfmade gear sometimes looks a bit clumsy, it often beats the hightech stuff. And the lightest gear sets I’ve seen were mostly self-made.