The funny thing about this thread is that the OP has actually used the term “pre-pay” in a way that is really exactly correct for what he’s talking about, though at odds with common usage. “Pre-” means before. “Pre-pay [pumping]” should be understood to mean pumping before paying. Yes, I know.
The problem with the OP is not the timeline, but the use of the word “allow.” Allow does not mean require.
Some petrol stations in Sydney require you to pay before pumping after a certain time at night.
I know. I’m saying it can be read as “What areas…allow pre-pay [pumping] for gasoline?” That is, where are you allowed to pump before (pre) paying.
Pre paying makes more sense to mean “paying before hand” or “cash up front”.
Slightly different subject but one thing that seems to be missing from US pumps is the ability to key in the maximum dollar amount you want at the pump.
I remember in New Zealand, if I only wanted $40 worth then I could key $40 into the keypad on the pump. The pump would stop at that amount. In the US, only the staff inside can do that.
Then the problem is that you’ve used the phrase “pre-pay” to describe the exact opposite of what it means, paying before you receive goods or services. At minimum you wanted, “What areas of the country/world still allow post-pay for gasoline?”
I have been to many gas stations that allowed pumping and then paying cash and they were in small towns and cities. I almost always pay at the pump with debit because I don’t carry cash most of the time. I have also seen pumps that took cash.
There’s a small independently owned gas station in my town. His pumps don’t accept payments and he does require you to prepay. HOWEVER, if he recognizes you, you can pump first. Luckily my red hair and the 20+ year old Jeep I usually have stand out so I haven’t had to prepay since my first time to his station.
I have also had people look at me strangely when I try to prepay.
Oh, I’m in MA and I frequently buy gas in RI, CT, and NY.
The last time I was at a station that did not require pre-payment was well over 20 years ago, somewhere in Nebraska along I-80.
All the thousands of times I’ve bought gas since then, the idea of being able to pump gas without having pre-paid or left a deposit is foreign.
Yeah, SoCal is always pre-pay. But I pay with a card since paying cash and going through the hassle the OP describes would just be ridiculous and unnecessary.
Since the gas prices started going up X years ago, most stations in central Virginia seem to require pre-pay. That’s when I started using my debit card because I’m not wasting my time going in twice to fill up my tank.
But there are still a few small stations that don’t require it and one doesn’t even have pumps that accept credit/debit cards.
Our local (UK) petrol station has a sign up claiming it’s part of a security network which registers numberplates (front and back over here) of anyone driving off without paying, and will flag you up so the pump will not activate. Not tested it.
And yeah, if you tried to pay in the UK before filling up (except at the pump by card) you would get some lovely weird looks. Might try it next time I need fuel, seems safer than testing the fill’n run security 
I’ve had a go with cash registers at a petrol station before, and I’m sure they wouldn’t be able to process it.
Oh, and I loved the NZ type-in-the-amount thing too, saves the humiliation of trying to pretend you really meant to put £20.01 into the tank. 