Over the past half century, gas stations have gone from gas only, to gas plus service (checking fluids), to self-serve, to 'smokes and cokes,' to having their own snack items (which actually have brand loyalty, unlike gas stations), to being like grocery stores
The younger generation is also reportedly more brand loyal to shops like these.
Gas sale itself is not very profitable (7% markup). Food makes up like 70% of profits now, reportedly.