Ha ha because our amazing government has never fairly funded national health service patients (people who can't afford private care...... which is nearly everyone) so all our hospitals are understaffed and waiting lists can be years long for simple operations.
As for the dentistry side of things, for the same reason dentists are overcrowded and refuse national health service patients treatment, only accepting private clients. This means that anyone who is on a low income or state benefits for whatever reason cannot recieve dental treatment purely because no dentist will accept them.
It is also worth pointing out that only very basic dental work is covered by the nhs, treatments to correct mis-shapen teeth (like a brace) replacing lost teeth or any work that is not required to stop pain is viewed as cosmetic and the full price will be charged regardless of your situation. For example if I can find a dentist willing to accept me I can have a filling for free but if I wanted my teeth straightened I would have to pay over £4000 for the course of treatment. I don't know many people who can spare that!
Sorry government rant coing on there......