Well, yeah, the primary purpose of gas taxes is actually to be a simple-to-collect use fee for public roads (sure, the match between "use of public roads" and "consumption of gas" is far from perfect, but it is -- and even moreso was at the time that gas taxes were first implemented -- a lot simpler than putting mile-by-mile toll stations on all public roads.)

So, to the extent that "impact on public roads" becomes more divorced from "consumption of gasoline", gas taxes get worse at performing their primary purpose (they still serve the secondary purpose of internalizing social costs associated with burning gasoline, but that's not their main purpose.)