Then you must have the weirdest waist ever, for a man.
I am able to go out into any store with my current waist size, and get a good-fitting pair virtually every time without even trying it on. Now, I may not like certain styles - I prefer my belt to be at my bellybutton, not halfway down my hips such that any erection can only ever point down - but men’s sizes are remarkably consistent.
Then that is an availability of options issue, and not any kind of issue where manufactures label a pair of pants to be a 38 when it is really a completely different size.
I bought several pairs of shorts recently from the same brand, all the same waist size, and some definitely fit better than others. There are always manufacturing variances.
I thought that too, until I actually measured my waist because I needed to buy some hunting pants online. I've worn the same size Levi's since I was 15 years old, and I figured that was my actual waist size. It's not. Measure yourself and compare it to the waist size of your jeans. They don't match up.