You're right, it's an absolute disgrace. This started in the 80s with the Tories allowing schools to sell off playing fields and a general de-focussing of PE within a centrally driven curriculum. The Tories of the 90s, Labour from 1997-2010 and the Coalition since have done absolutely nothing of substance to turn that around. Admittedly, Labour did try to change this with the "Building Schools for the Future" scheme but this over-used PFI and created only a tiny handful of fantastic new schools that had sport built-in; the Coalition scrapped this immediately though mocking it as "overambitious", a great idea thoroughly sabotaged by political insiders in Labour and then trashed by that cretin Gove.
The school I attended in the 80s had 8/9 full sized sport pitches, athletic track, tennis courts, a small swimming pool and so on, they PFI'd up to get a new school and part of the deal saw the school being built over two pitches, they retained one pitch and sold absolutely everything else to the developer as part of the deal, that one remaining pitch is a permanent football pitch with no space around it for athletics.
It's not all government's fault though, the increasingly litigious nature of society means that you just don't get non-PE teachers helping out as 2nd/3rd team coaches any longer. Insurance is a nightmare for many schools and they can cut huge percentages off their insurance bill just by dropping any mention of "rugby" from their school's sporting curriculum; for most schools if they received competitive quotes for insurance with a side-by-side comparison, one with rugby (either code), one without then they'd have a massive fight to keep the sport going.
Rugby union responded to this in the mid-90s with a massive investment in club youth development, providing free equipment, free coaching courses, heavily discounted insurance and so on. The RFU, SRU and WRU all grasped quite quickly that either they retreated back to the fee-paying schools or they took it out of the hands of the schooling system with their arbitrary "initiatives" based on the political annoying person in charge at the time. Rugby league has done much of the opposite in the last couple of years with, for example, the removal of RFL funded development officers, there are now almost no incentives for a RL club to run a youth setup, the better kids will get snatched up into the academies and never look back and the other local clubs without a youth setup will just throw money they don't have at young adult players to get them to come play. Even then, the in-fighting in the sport means that it's just down to the stubbornness and sheer will to continue among the clubs with youth setups that keep the youth game alive.