I'm afraid one part of the answer is very simple. In the southern part of the UK there are very few days with snow. A snow plough/brush/blower device costs in the region of £400,000 and they come in packs - five or six at a time and an airport like LHR might require 20 or so of theses machines. Each has to be crewed and the drivers trained. In addition, stockpiles of chemicals (with 'best before dates') have to be built up and stored somewhere. And we also have to make it possible for the people who perform the snow clearing to get to work. This has to be paid for by the passengers who use the airport. To ensure a 'worthwhile' response, someone has to sign off several millions of pounds every year - and I think they are probably correct in not doing do.
The remaining part of the answer is responsibility. Historically, UK airports are very reluctant to offer pilots up to date braking action reports - so as soon as any contamination occurs, those who should be able to provide information develop a severe case of 'sloping shoulders'. So unless the runway is cleared 'back to black' the runway becomes effectively unusable because nobody wants to take responsibility for passing on any information which they might become financially liable for. Yet another of the costs of living in a compensation culture.
Solutions: Pay more for your ticket and strangle anyone who thinks compo lawyers are good people.
PM