People will only stop trading btc to fiat if they have to buy something exclusively with bitcoin.
Otherwise it's still more advantageous to exchange btc to fiat, as you buy anything with fiat, and with bitcoin only few goods and services.
In some countries, for instance, in Germany, Bitcoin can be used to buy things. If you are a traveler and BTC holder, it is better not to convert crypto in cash and travel with any sums on your account (in Bitcoin wallet is this case).