Why do gas fees exist in the first place?

Noob here... was wondering, since it seems theyre the pain of the era, why do gas fees exist at all?

Is it to support the miners? Isn't the currency itself reward for it?

Is it to support the services / platforms / processors? If so how is this then decentralizing? (Arguably sooner or later big players will pop up who can dump or siphon the prices and pipeline to them).

Is it to make things smoother all arround? Why?

I guess my main question would be - can, would the Eth, and others, survive without gas fees? Why have them? What's their benefit?