>there is no guarantee of return, or even the promise of return
You should check out some altcoin subreddits and /biz/ and I think you might disagree with yourself.
"Frgtpsswrdlame-coin is going to the moon! You guys need to hop onto this, I already have a 100% return. Plus it's safe because frgtpsswrdlame-coin has <encryption gibberish>. It's still early so get in!"
"Buy the dip! If you look at frgtpsswrdlame-coin's charts you can see that there's a <technical analysis gibberish> pattern forming which means this is going to bounce right back!"
Perhaps what seperates this from a more traditional pyramid scheme like door-to-door knife sales is that you can't point to the guy who convinced you to buy in and you can't point to the guys at the top of the hierarchy but they still exist and they still misled you. It's just obfuscated because of the internet.
Look, every Ponzi that ever existed has anecdotes about those who made it big--it's part of the con. Getting rich quick is the dream of every peon everywhere.
As OP pointed out, everyone who is investing in mining / purchasing these coins is hoping they will be a store of value that will appreciate. At some level, it's no different from betting on specific commodities. No one is promising anything. I think that's an important distinction.