Liquidity.

Bitcoin is a good store of value but not a good currency because of its volatility.

Businesses need credit for flexible liquidity (IOU's)

Accounting for Bitcoin price flux is....annoying. Having to pay taxes on something that was 69k but is now 26k.

It's why stable coins are popular.

People need to have a real physical presence, with real accountability to the state (aggression/taxation) in the real world.

This article by a bitcoin dev i recently came across does a good explanation :