This was the norm during my childhood (90s and 00s). Paying at the pump is a fairly recent development. I think gas stations were reluctant to adopt it because it makes it harder to sell snacks.
I live in Australia now, and all the servos (gas stations) I've encountered here are just like the American gas stations I grew up with: you pump, then go inside to pay. The only real difference is that adding air to your tires is always free here.
> just like the American gas stations I grew up with: you pump, then go inside to pay
Within the similar timeframe I've always encountered the three-step process: you go inside and pre-pay, back out to pump, then back in to get your change (if you didn't just load $20 onto the pump and use it all, anyway). Even the 'pay inside' button on the pumps just flashes "See attendant" on the screen. Same when I worked at gas stations during the downturn. The only places I've ever found that'll let you pump before paying have been the most rural lil independent stations. Gotta love the varied experiences across this bigass country.
As recently as 2019 I would refuse to purchase gasoline at a station that was pay-before-pump. There were enough options. This is no longer the case sadly.
They're usually card-based. You insert (or in past decades swipe) your card, a hold gets put on your account, you pump the gas, and the measured amount gets removed from your account & the hold removed. If you don't have enough in your account for the hold, the transaction declines. It's effectively pre-pay, even though the transaction settlement doesn't happen until after the gas is pumped.