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.
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.
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.