The fees don’t increase if the price of btc increase. Fees are not related to the price of btc, but rather to how many people are making transactions on layer 1 on chain (many people want to transact on layer 1 = high fees).
They do say that one day mostly (mostly, not only) big entities will use layer 1 on chain to transact (because they are the guys who move millions and billions and they need to do it within a certain time frame, and so it makes sense to pay a high fee for them given their situation). But even in that scenario a normal nobody pleb is still incentivized to run a node because:
1) you want to verify yourself with your node that your utxo are real (if you use somebody else node you are trusting somebody else telling you “yes you have these utxo with these amounts”)
2) it is still in your best interest to make the btc network as decentralized as possible and not to trust others to do it for you (especially big entities, because they have never fucked as over in the past/present right?)
3) if there is some dispute in the bitcoin community (like for example now with core/knots) running a node is your way to “vote” in the bitcoin network (you got no node? You don’t get to vote)
