Even today, we all know that there are many gun owners that wait until a panic to get a gun, magazines, and ammo.
Back in the late 80's and 90's there were a lot fewer semi-autos out there compared to now. Yes, there were many available, but they just were not as widely seen and used as today. The '89 ban on importing semi-autos was a hint of things to come, but there was much less of a concept of stocking up back then. Then the '94 ban hit, and magazines shot up in price. Many guys here have written about their work-arounds during that time, but even the internet was not as developed back then, so if there were strategies to obtain magazines, they were less well known.
I didn't know any neat tricks then to order mags from overseas or anything, so I was stuck with what I had. Fortunately I normally had around 4 or 5 mags for a gun when the ban started, and I remember ordering 15 East German AK mags for $100 in the mid 90's. I didn't think I'd ever need another 15 AK mags at the time, but it was so cheap I just did it. Since it was unsure that the ban would really end someday, I mostly used 10 round mags, and saved the higher capacity mags. Except AR mags. I was not a high volume shooter, and I had a good supply of AR mags.
Being in the army back then, there were surplus stores around most bases that sold gear, and you could often find used military mags for around $10 (like Ranger Joe's outside of Fort Benning). The 30 round mags made at the time said "LE Only", but when I came across pre-ban mags I got them. So I always had a good supply of AR mags, and for other guns a not-so-good supply because I could not afford to spend $100 on more mags.
Once the ban ended and magazines became inexpensive again, anyone that did not stock up that lived through those years has no excuse, but we all know that there will always be plenty of people that fail to prepare even minimally. At the other extreme are those that have cases and cases of mags.