@pitiflin: I agree with most of what you wrote, only that I'm a bit less pessimistic, it seems.
I wholeheartedly agree that I am a pessimist, but there's reason here, explained below:
Maybe because otherwise it could fall again into complete irrelevance, e.g. 100$=1 BTC? Then they would get
poor from it

Think about it, if people start using bitcoin as a currency, there would be more supply for it, since it has a high monetary value. But the demand will be very low. We would see the same blackmarketing strategies applied here, this time its only legal. And an economic theory/principle known as chain effect will occur here. Either the price will go down and the demand will go up. Or the price will stay as is, and the supply would fall down, causing hoarding, or as in this case, hodling, and demand will go up. Either way, price will go down, if mass adoption occurs.
While you're right that a massive adoption would need a mentality change, I guess a massive usability boost (by easy to use LN apps, for example) can be a significant factor for that to happen.
And for the hodlers not wanting to spend their "precious" BTC that
could make them rich: Have you seen
davis196's proposal for merchants to give a kind of "refund bonus" in bull markets? That could end in a win-win situation (for buyer/BTC user and merchant), see
my comment on it.
There are use cases for Bitcoin where it already really
excels, but still isn't used massively. The biggest area imo is remittances (I have used it often for that purpose as I've a migration background). I guess spreading the word to use BTC-based services instead of Western Union and friends is a good idea as people can save a large part of the fees.
This whole refund bonus would only work in a short term, couple of years later(more or less the same), people will again go back to point 1 and become hodlers and bitcoin into an investment. Something that could really change the situation is, satoshi coming back. He is the one who would be able to make people realize what bitcoin's actual purpose is.