Based on your previous posts, it appears it was a "chain and freewheel" that were worn out. I expect neither of them were very high quality--probably the cheapest ones they could source, as that's very common on these types of bikes.
It does not cost very much to get good quality parts to replace them with--but depending on the design of the drive, and the size of the chainrings used, they may wear faster than they should simply becuase they might not be sized correctly. Larger chainrings would mitigate the wear on them, and proper tension may help wear on the chain itself.
Additionally, if the gears are shiftable, and you are not shifting up and down to the proper gear ratios (or if they did not include the correct ratios for startup/etc), it will put extra strain and wear on the chain and chainrings, as well as the freewheel mechanism itself on the rear wheel.
Also, if there is grit or any other road debris or dust that gets on the chainrings and/or chain, it will wear them much faster, and so it may be better to run a waxed chain rather than oiled (see the various pages on that at the http://sheldonbrown.com website). Or if the chain has no lubrication, it will also wear faster.
With cheapest-level parts, those things will typically spell a quick doom to them, but not necessarily--I've used even crappy parts under heavy abuse way beyond their ratings and not worn them out--destroyed them in accidents or abused them to breaking point, yes.
With better parts, under proper use and maintenance conditions, they can last for thousands of miles. But these are all still parts intended to be replaced after a time, just like various parts in cars such as timing chains and whatnot--while they will still "work" after being worn down, they wont' work quite as well as when they were new, so replacing them at specific intervals is often recommended.
In cars, almost no one actually does this maintenance, until the car ceases to run or run reliably. The same is true with bicycles. The car parts are made larger and heavier to handle the strains of the power they use, and the bicycle parts are usually made lighter for ease of riding under only human power, so unless the proper heavier-duty parts are used for powertrain parts, then if higher power levels are used, or if they are used harder than under typical human power levels, they will wear faster than normal.
Again, the bicycles can do what you want, but you have to use parts intended for the purpose, and design the system to work within the limits of the parts. Unforutnatly the majority of premade ebike companies don't do that, becuase of cost--the same is true for most human-powered bicycle companies, too.
Go buy a $150 bicycle from Walmart and see if it lasts more than a few hundred miles without parts falling off
and then keep in mind most of the ebikes companies make these days are of the same quality, both in electric and mechanical components.
Go buy a *used* $300 bicycle from a good bike shop and ride it around for a few thousand miles, and see which parts you need to replace--probably not much besides tires and/or tubes and brake pads, whcih are all normal things to wear out.
Even some of the well-used medium-level bicycles I've found at thrift stores for $20 and used heavily over the years have not had any problems other than tires tubes and brake pads, despite the intense mileage.
As to whether these things could prevent them from replacing cars? That all depends on the end-user, really, and their needs and uses and conditions where they are.
