Unlimited internet has been a welcome respite from the inconsistent and unfair pricing of mobile data plans. Seeing that change without an explanation feels wrong.
I can imagine ISPs responding with "Here's your explanation: our infrastructure isn't built out to have everyone downloading 1TB/mo and if you want that you need to pay for it"
To whatever extent that's true, it's because of an ISP oligopoly and active lobbying measures that prevent creative solutions that might improve quality/decrease costs.
So I'm personally upset over this because it's a nickel-and-diming false choice between paying even more than our already-overpriced bills, or watching your quality of service decrease because a greedy company decided not to keep up with an eminently reasonable change in standards of quality.