Security cameras existed, but they very frequently didn't work. One of my college professors was murdered in a bank robbery around 20 years ago. The bank technically had cameras, but they didn't work and no one bothered to do anything about it. Consequently, there was no recording of the robbery and the police chose not to investigate the crime.
I mean, after the Oklahoma City bombing in 1995 I remember seeing many video clips of the vehicle making its way to the building. Checking now, https://libertarianinstitute.org/articles/the-oklahoma-city-... says "A 1999 Freedom of Information Act lawsuit filed by investigative journalist David Hoffman revealed that the FBI had twenty-two video surveillance recordings of the Murrah building and surrounding area stored at the FBI’s Oklahoma City field office." Its Wikipedia entry links to https://web.archive.org/web/20170510090822/http://newsok.com... saying "Agents also examined more than 900 security videotapes".
If most cameras 'very frequently didn't work' then that means there were huge amounts of non-working cameras in the area. Which seems like an expensive waste of money.
I can well believe that some cameras didn't work - I already mentioned the bank robbery where the cameras had run out film months previously.
In any case, the original claim "No cameras 20-30 years ago" is simply not true.
And yet, think of all the servers that get hacked today because they are running unpatched versions of their operating systems. I agree with you that there were lots of CCTV systems 30 years ago. I'm just pointing out that the fact these cameras exist doesn't mean they are maintained or that employees know how to use them, and that this problem was more challenging in the past because stuff was mechanical and analog and not as easy to automate.
There's quite a range of gas stations, so it's hard to be certain about any specific one.
But a gas station for a major chain seems exactly the place that would have working cameras, because you're going to get people who fill up and drive away without paying.
It's really hard to know if my memory is faulty, so I looked for images of gas stations from the 1990s.
On the other hand, the five or so other US stations I found, from the same time frame, don't have an apparent camera. (Which doesn't mean they weren't there, though that seems unlikely.)
So .. I don't know. But I can say that at least some gas stations had video cameras going, and I don't place much weight in your argument that they "very frequently didn't work".
In the mid-1990s someone had a fender bender with a co-worker's car in the parking lot. The building had roof cameras, and he was able to get security to review the video the next day. However, it didn't have the detail for that purpose. So my anecdotal evidence is that it wasn't all that hard to have a working system 20+ years ago.
After all, it wasn't all that expensive for Jennicam to get started at that time, with automatic image capture and uploads.
