Nobody know how to change it or turn it off. That means a lot of developers and advertisers assume it is actually a good way to track users. So if you go in and reset/disable it, you'll be in such a small minority that you'd become an edge case and they'd lose the historical data on you.
Obviously this isn't true 100% of the time but if it didn't exist then advertisers would use a hardware fingerprint probably, which is a lot harder to spoof