1) My debit card doesn't cost me anything to use. Buying Bitcoin costs me 1% or more to get and that's if the price hasn't crashed by the time it clears Coinbase. So, accepting all that risk, paying more and maybe getting a discount, is a non-starter.
As with any new technology, there will be early adopters, late adopters, and everyone-in-between adopters. You're looking at things from the viewpoint of those who will be the late adopters. Fine, someone's gotta be last. The early adopters will think that sure, the price may crash, but then again it may go up too, the latter being more likely. And as time goes on, the volatility will decrease. You say maybe getting a discount. In fact they'll either get one or they won't, and if they do, they'll know it. The merchant, who HATES paying credit card fees, is incentivized to market bitcoin to them so that the merchant can avoid the credit card fees.
2) Porn? Is that really the best you can come up with. 
It's not the only example I can come up with. But it's a damn good one. So in the words of Ron Burgundy: "Don't pretend that you're not impressed!" ....
PS It's a good example for two reasons:
1) Easy to understand the motivation for someone using bitcoin. No esoteric economic arguments needed. In fact, I think even Dogecoin community would get it ... Such motivation. Much privacy. Wow.
2) Historically, much of the early growth of the Internet was through porn. Like it or not, if it catches on in the porn industry, it helps lay the groundwork for more mainstream uses.
