Why not?
.W.
Discussions I had with both Michelin in UK and Land Rover engineers when I worked there, both said fitting tubes to wheels ( with Humps) designed for radial tubeless tyres is not recommended due to the potential for a catastrophic deflation. This is due to the high pressures required to seat the tyres when fitting, to get the bead to "jump" over the humps. We have all probably noticed the bang when this happens . When a tube is fitted it starts to grip the case of the tyre as it is inflated and in the case of wheels with humps the pressure can be such the tube cannot slip around as the bead jumps over the hump and it can be locally stretched beyond its elastic limit and create a localised weak spot . As the engineer said , if it immediately fails , you know there is a problem , but if it doesn't, it could fail at a later time especially when the vehicle is carrying out a violent evasive manoeuvre, exactly the time you don't want it to.
There is no way of checking, so the recommendation is don't do it. I. I am sure there are many tyres fitted with tubes on tubeless wheels without an apparent issue but I for one wont do it.
Conversely, during the same conversation I was advised that if you fit radial tyres to wheels without humps, a tube should always be fitted, as the grip on the road afforded by radials means the tyre can be pulled off the rim with catastrophic deflation if one isn't fitted.