No matter how you cut or transfer bitcoin, your answer is still a tautology. And if the only reason you trade things you can live off of for BTC is because you can sell BTC based on faith, that reason is irrational.
Again, what's irrational and what's not is not down to you to decide.
"Future purchasing power" is irrelevant. I care only that I'll own things I can live off of. Whether this is minus a few percent doesn't bother me.
What if I told you that it's irrational to not care about inflation? What if I told you that I do care if it's minus a “few” percent?
Why then would I pay even a dime for these features and utilities? Moreover, I can have as many coins as I like. Why would I pay $40K for a single coin if I can have the whole package for free?
Because you can't. Setting up your own altcoin means you're outside Bitcoin, where everybody agrees. You still haven't acknowledged that Bitcoin is worth so much, because of
consensus. You can't comprehend that this is what people evaluate and not numbers in a database.
I am not deciding what's irrational and what's not, the logical syllogisms do that.
To not care about small inflation is not irrational because costs of maintaining physical assets are much higher. Also assets like vehicles are worth less with time. What is really irrational is to replace a system where someone is liable do give you things you can live off of and where this liability is secured with physical assets for a system where you have only faith that unknown people will voluntarily give you such things.
Regarding the last point. It is irrelevant what others people comprehend. That's just something that is going on in their minds. What is relevant are things you can live off of.