That's a good point, actually.
Another thing about gas taxes is that the move is towards migrating motor vehicle powertrains to electric. Once there is a fair mix of electric and gas/diesel vehicles on the road, then the tax is only penalizing those who haven't or can't afford to switch over to new electric vehicles. It would not function as a deterrent to traffic, as Colin alludes to, rather just a revenue grab from a specific portion of the public.