Here in British Columbia, we have all kinds of laws and regs.
Here is a link, much easier than trying to write it out.
https://www.icbc.com/driver-licensing/types-licences/Pages/Licence-classes-and-types.aspx
If the vehicle has air, you need the endorsement.
If you are pulling a heavy trailer, you need the endorsement
If you are pulling a heavy RV trailer, there is an endorsement for that
The commercial guys will get checked during random vehicle check.
So Grandpa must have his air endorsement.
Or
If Grandpa decides to pull that 40 foot 5th wheel behind him, he must have that endorsement also.
But I dare you to go to one of our RV lots and have the salesman tell you that.
Where I live we don't have scales, closest one is about 120 km away (70 miles roughly) so you will see lots of stupid things going on. Not so much on the big guys, but more like what DMiller posted about.
The commercial vehicle inspector is mobile in our parts but he has to catch these looney toons that think they can pull a mini ex behind a toyota pickup ( I'm exaggerating here), but you know what I mean.
The problem is, unless you get pulled over or are involved in an accident,
NO ONE ever asks if you have the proper endorsement.