Although true, it isn't the point I'm trying to get across. My view is that weight limits aren't a great metric. You don't have to go for niche sports, the traditional xc/trail bike is what everybody starts with on mtb.

Say this example xc bike has a weight limit of 150Kg. Rider A is at 170Kg buys this bike ignoring the limit and just rides smooth local fire roads for some excersise.

Rider B is young, athletic 70Kg build. Buys this SAME bike and goes on rides with friends that know all the fun trails. Rider B is getting faster and stronger, and the bike starts to show it's limitations.

It's clear which bike will fail sooner. Weight alone doesn't matter, and both riders are using the bike for it's intended and designed purpose.

Manufacturers cannot reliably slap a max weight to their bikes because of all the other factors involved. And if they do, it will be way conservative to avoid getting into legal trouble.