Ofcom allowed the networks to switch to the CPI+nn% formula. The nn% was supposedly to allow further investment (as if the general income from bills wasn't enough) and in return, they'd all offer 30 day and 12 month contracts and 'essentials' plans for poorer users, as well as other incentives (like discounts for NHS etc).
I have no idea how many people are on the low user plans, or if anyone can get one (or need to qualify), but they were very quick to come up with a figure to add on to CPI.. and wouldn't you know it, they all concluded that for their own individual needs it would be 3.9%. I guess 4% sounded too greedy. Cartel anyone?
Ofcom got played.. just as Ofgem got played into allowing service charges to be pretty much whatever an energy supplier wants as long as they offer some help to poorer users.
And as discussed elsewhere, gyms are allowed some rather exceptional T&Cs in contracts by today's standards on consumer protections, because they do offer some people cheap memberships.
Regulators are useless. They try and sound like they're on our side, but they're either in cahoots with the businesses or just tricked. Either way, they're pointless most of the time.