This did not work for every user - for example my buddy bought an Asus Zenfone 2 (ZE551ML) specifically to play this game. I warned him not to buy from a China seller but he proceeded because he was finding guides that told him it was a great phone for the game - he literally bought this phone to play this game.
I attempted to remove root however this has now forced the phone to be stuck on Edge network (he can play but now only on WiFi :/) I have attempted to re-flash the physical ROM's (as well as the recovery matching those ROMs) from ASUS (successfully) and it still is stuck on edge. I've contacted his phone company (T-mobile) - insured the proper bands were being requested, 5x checked the APN settings and yet the phone still doesn't want to connect past edge. Here is the kicker, I scan for nearby cellular networks and T-Mobile (LTE) shows up, the phone registers, yet still won't obtain the connection.
Honestly that issue is probably due to some other restriction but it shows the frustration some users have had to deal with because of this move.
I even tried re-rooting the phone just to get his network back because he'd rather have his phone than Pokemon GO yet the phone had something special done to it to allow the network to work under root.
No one should have to go to those extremes especially when they aren't cheating and they are a paying customer.
In all honesty I don't believe the ban on root was done to deter hacking - my belief is that it was done because on average users only root because they want paid apps for free (a lot claim it's to tweak the UI and remove bloatware, but as more and more phone's get released we are starting to see this less and less of a requirement). While many rooted players (due to pre-rooting) are actually paying customers it still doesn't outweigh the paying customers who are not rooted and therefore it was more then likely a move to remove users who are less likely to put money into the game.
Every move they have done really reflects that they only want more money with the least amount of work and that is why I only keep the game installed to keep my 1 star reviewed from being weighted down due to being a review for an older version.
One of the big guys who is involved in creating a usable tracking system via a third-party map has made a wonderful statement about the many failures of Niantic [1]. From unnecessary obfuscation that only slows down older models, to banning the devices that aren't the reason cheating is happening, to not creating a good way to achieve feedback (apart from "critical errors" which is built into the app - maybe I should start complaining about the critical "Niantic" bug and that it needs to be fixed ASAP, but complaining won't really get anywhere if the company isn't listening to those problems) Niantic truly is on a path to destruction and I hope Nintendo doesn't let this amazing idea die if Niantic falls.
It really doesn't make sense to why they are making these decisions. The developers should know that banning rooted devices won't deter hackers - in fact I would have to say it's grown a few hackers/cheaters due to the frustration of dealing with lack of communication and oddly made decisions.
[1] http://www.twitlonger.com/show/n_1sp6pkg