I think they were also a LOT more hard to get hold of (and paint) back in the day.1st and 2nd edition we never bothered. I think that was because combats were less tactical in their execution. The D20 system changed all that and battle map with minis became a necessity. We've stuck with them ever since.
D&D painted plastic minis made a big difference when they arrived 22 years ago, and youtube painting tutorials also opened up the world to a lot of people. (The cost of the Wizkids minis now is absolutely shocking to me).
Cheers!