Disposable vapes use C grade lithium batteries that are otherwise low quality and would have been discarded anyway since they're already mostly used and not good enough to go into any other applications.
I find it immensely telling that the vast majority of these things (ie. the popular flavoured kinds) are banned in the country that produces them.
This is the dirty secret regarding lithium cells.
At the very least, using C grade cells in this manner ensures a working product gets used for some application even if it is disposable.
Take solice in the fact that when you throw batteries out in landfill trash that most are picked up by high powered magnets and are separated out for recycling.