Saving in BTC vs productive assest?

Hey everyone,

i see a lot, that it is recommended to save your money in bitcoin. (sometimes entirely)

I can see where bitcoin is better (far better) than gold due its transparency and scarcity and with lightning could be extinguishing for fiat payments. I like it.

But what i cant understand is: Why should i, for the long run, put my money there? If i place it in an diversified worldwide economy tracking funds, i dont have to care if i pay everything in 40 years in sats oder something but my money would work and i would participate in newly generated products and services aorund the world.

When i would have btc its like a non productive asset. Why should i rather save in btc than in productive diversified world economy parts?

Thanks a lot in advance!!