If there were no exchanges, then you may have some point. Since you can exchange any amount of fiat for bitcoin in seconds/minutes (and non-KYC in minutes/hours) the whole "I'm not spending bitcoin because I only want to spend fiat and hoard bitcoin" is quite meaningless. Just exchange fiat for whatever is your target to have in bitcoin and that's it. Spending or not spending bitcoin doesn't have any meaningful effect on how much bitcoin you have if you use exchange. You can do "spend and replace", which is essentially a mind trick, but it may work as a bridge for some people.