I've already made a comment on this and there are some interesting comments on the Heritage Action site which are worth reading (for anyone who hasn't).
English Heritage probably fear a riot if they stop people having access at the winter and summer solstices. The Druids think it is their right although everyone knows now it isn't. The word etiquette springs to mind - if only all the people attending gatherings were collectively respectful.

This comment caused a wry smile.
"Pull it down! Get on with your lives! That’s what the Ancients did 4,000 years ago… they abandonded (sic) it as meaningless. And got on with the Bronze Age. Stop living in The Past!"

Edit: Just seen this too - well done HA.
http://www.bbc.co.uk/news/uk-england-wiltshire-31584718