Vortexadminman - if you gave them winches, they would need bigger and more expensive helicopters plus a load of extra training. Rega (the Swiss outfit) use either EC 145s or A109 K2s, whereas most UK AAs have smaller machines like 105s, 135s or 520s.
In order to pay for the extra capability they would either have to raise far more money from donations (more tricky in a worsening economic climate) or charge for their services. For the number of occasions when it would pay dividends it is probably not economically viable.