For a petrol station. There's nothing to cannibalize. They can either watch all the EVs drive past to the next charging + pit stop opportunity or accommodate those customers and have them in their shops, rest rooms, restaurants, etc. Petrol isn't their core business in any case.
Easy choice if you want the business. The rest is just economical Darwinism. Anyone driving a car for work is likely to be switching sooner rather than later; in some countries that process is already pretty far completed with e.g. leasing companies preferring evs for cost and other reasons. EV sales have hit double digit percentages in many countries and the number of countries where that is over 50% is also growing. So, easy choice for most petrol stations. More a question of when and how many than if for most of them.
It’s like saying telecoms won’t provide internet services because it might eat into SMS and phone call fees. So far that hasn’t been true - where I stay at least.
This has definitely happened, worldwide, and it's still happening. Crap mobile internet quotas, for example.
It's probably better to cannibalize your own market share than have the revenue go to a competitor.