Generally speaking, it's becuase there's no privacy mechanism with a static address.

Silent Payments changes this, however it's still being fleshed out.

Not saying that direct deposit is better but for most use cases it's more convenient.

That being said also tools like Bitwage exist.

I think the biggest fear with Bitcoin is most people don't get big enough wages that would necessarily benefit from it as a wage.

I think most people prefer paying fiat bills with fiat, and buying Bitcoin with the leftover money since currently it's the more convenient, and cheaper option.