So just a "hunch" and nothing else. Interesting.
There is plenty of evidence to support it. Take a look at the ipv4. That is a pretty messed up situation. Charging board could come into contact with something and short out. Take a look at all the 50w isticks that were catching fire.
I'm sure I could find a case where an external charger has caused a meltdown or fire and then what? Are LiPo batteries basically a ticking time bomb?
Essentially, yes. They are not the safest batteries out there. Minor issues can cause major problems. At least if your battery destroys your charger, your charger got destroyed instead of the mod. Why anyone would want to risk ruining a mod that likely costs double what the charger costs is beyond me.
Again, how many cases of iSticks blowing up from being charged? How many of these issues with on board charging of external batteries is because of user error (incorrect or damaged battery)?
Quite a lot of the isticks caught fire.
At the end of the day, it all boils down to this:
-A quality, dedicated charger has been designed with one purpose in mind: to charge batteries.
-A mod is designed to be used with an atomizer so we can vape. The charging circuit isn't the primary focus of the device.