Supposedly it's about closing the pores. I kinda think it's a myth level thing.

Now, a good moisturizer to keep the skin nice, and maybe a little something to reduce shave irritation is good thing, but that's not where aftershave got its start in the form this post is talking about.

That kind of aftershave, ala aquavelva is a fairly recent thing, having come into existence during the early 1900s. There were absolutely other aftershave products before that, at least as far back as the 1700s, and they often contained alcohol (along with other lovely things like potassium cyanide), but it wasn't quite the same thing.

Before that era you still had things used after shaving, usually to reduce irritation. There's records in Egypt going back to B.C. eras describing the use of oils and balms for such. Same in China, India, pretty much anywhere people shaved amd kept written records of some kind.

But the advent of what we think of as aftershave when speaking english came around after affordable steel razors matched up with a general social trend that made shaving the default. Alas, those razors were not always well made or well maintained, and there is a skill to shaving with them. So skin irritation was a common thing, hence the market booming.

Nowadays, people have realized that dumping a liquid that dries out skin (alcohol) onto freshly scraped flesh is not ideal. So we have better options ( not surprisingly, the trend is to things closer to the centuries old supplies than anything else)

A good safety razor, disposable multi-blade, or well maintained electric razor aren't going to abuse skin much, assuming basic care is taken. Even a well kept straight razor and some practice can give a clean, low-to-no irritation shave, though the learning curve is still there for both the shaving and the razor maintenance.

If one's skin isn't bothered by the shave, bothering with products afterwards is not necessary, though it can be pleasant