Because it isn't. The pricing, timetables and services were basically all centrally controlled. The train operators put in requests to change them, then the go

Because it isn't. The pricing, timetables and services were basically all centrally controlled. The train operators put in requests to change them, then the government (or Network Rail or whoever they delegated the power to) would approve/deny them. Since they're sharing access to the underlying infrastructure, they can't do what they want. Additionally, there are many trains that are unprofitable but the operators are required by law to run them for public interest reasons. When they designed the franchising system, they tried to "balance" each franchise so it had roughly the same number of profitable and unprofitable routes. The idea that our existing franchising system was anything remotely resembling free market is absurd. Then on top of that, because decision making and control was distributed amongst 40 or so different corporate entities, trying to make a change to the ticketing system was damn near impossible. If anything, this new concession-like system will likely be more competitive, even if the government is acting as an intermediary.