When talking with your manager about a promotion to a more senior position, how do you answer "why should we promote you?"

What's in it for the company? I could say "promoting me shows all employees that this company offers career growth possibilities, and that hard work & taking ownership is rewarded" - but maybe that's a bit cheesy?

I don't want to go "if you don't, I'll have to change companies", that sounds too threatening.

What other interesting reasons could there be?