Disposable vapes are indefensible. Many, or maybe most, of them contain rechargeable lithium-ion batteries, but manufacturers prefer to sell new ones.
To make a point about how wasteful this practice is—and to also make a pretty rad project and video—Chris Doel took 130 disposable vape batteries (the bigger “3,500 puff” types with model 20400 cells) found littered at a music festival and converted them into a 48-volt, 1,500-watt e-bike battery, one that powered an e-bike with almost no pedaling more than 20 miles. You can see the whole build and watch Doel zoom along trails on his YouTube video.
Proprietary spare parts. The motors might be off the shelf so you could grab parts from a different manufacturer. But controllers and batteries are usually proprietary making repairs much more complicated and cost-inefficient