I can imagine, one reason is due to hygiene. The lotion is in bottles and closed, but a toothbrush, you will use in your mouth, a more sensitive part, where some people cares about things like hygiene more, that using a lotion, although it is wrapped in a box ore anything like this.

I know several people, who do not use the toothbrushes in planes because of hygiene reasons, they bring their own.

And the most hotels offer them on request, also the low budget hotel like Ibis, Etap or Express by Holiday-Inn.

Refill those empty travel size tubes
 

Just hold the tubes nozzel to nozzel (picture the space shuttle, docking with the space station) and squeeze the big tube. This works best if the big tube is full or folded down, as a little pressure is needed to push the tooth paste into the travel size tube.

Avoid the high cost per brushing of the travel size tube and helps keep our planets landfills from overflowing with empty travel size tubes. :rolleyes: