[pwg]

> Both are reset with factory reset, but apps still for some reason demand tracking via IMEI.

Because from the marketers perspective, a fixed, constant, identifier of a particular phone beats out one that can change periodically. There's more tracking and big-data possibilities from the fixed never changing IMEI value. So that is what they want.

[Aissen]

Except you probably want the reset anyway, since most normal people don't factory reset unless the phone changes owner.

[pwg]

What I personally would want is no way for any advertiser to ever send any ad to my phone in any way, ever.

But given that I'll not likely ever reach that point, I'd settle for those advertisers not receiving any unique identifier from my phone that allows them to know anything more than "ad X was sent to an anonymous phone".