Willfully getting chickenpox to develop 'natural immunity' to it is one of the dumbest things ever.
The virus has a good chance remaining in your nervous system (which your immune system can't get to). It then has a good chance to reappear throughout one's life, causing very painful shingles.
Or, you can get the vaccine and have a good chance of ever allowing the virus to take up residence in your nervous system.
People are talking about 25-30 years ago - before the internet as we know it made everyone "medical experts", before the vaccine was even approved in the US for children in the mid-90's - and it didn't become standard immediately, even then.
The thought of vaccinating against it is very much a millennial-generation thing. This connection between chicken pox and shingles was known to the medical research community, but was not commonly discussed knowledge among the public (likely, and particularly, because there wasn't anything at the time one could do about it anyway, as everyone was pretty much expected to get chicken pox eventually). It didn't become part of the mainstream discussion until the vaccinations began and people would ask "why on Earth would you bother to vaccinate against something like chicken pox?" because it was seen as an annoying, but innocuous, "childhood disease" - just part of growing up.
The conventional wisdom up until that point was that parents
hoped their kids got it early just to get it over with - because the later in childhood you got it, the sicker you would get - and it
was well-known that if you somehow managed to make it through until adulthood before you got it, there even worse complications. I personally didn't get it until junior high, and the pox itself was mildly annoying, it was getting really sick to go along with it that sucked.
Heck, this train of thought was so common to even become a television trope - "oh look, one of the kids got exposed to chicken pox, someone is going to get itchy! guess who gets a few days off of school? grab the calamine lotion!", only to find out that one of the adults in the household had somehow miraculously never had it, which led to isolation/genuine concern/sitcom hijinks, depending on the format. (Though, I believe Brady Bunch did it first with the measles, which at that time was also seen in much the same way as chicken pox by the general public.)
In today's instant access internet society, this may all seem crazy - but remember, it wasn't that long ago that humans didn't spend big chunks of their day reading data online, and mostly relied on what they had been told growing up.