Money is a thing that one person gives to someone else as payment.

Why does it have to be a thing?

Because if it is not a thing, I cannot give it to someone else.

Rather than give you money, I can teach you to play the electric bass guitar. You might accept that service as payment, but my "lesson" is not money except in a very loose metaphorical sense. You are unlikely to be able to buy groceries by transferring to the clerk the first electric bass guitar lesson which you already received from me.

Bitcoin is not money because Bitcoin is not a thing. Perhaps like my electric bass guitar lesson it is tremendously valuable. Perhaps it is worthless. But it cannot be money any more than trade can be potatoes.