They have them at the Aberdeenshire circles too - they're usually a way away except at places like MidMar - but that's surrounded by tombstones anyway. Those are more informative than prescriptive and are quite nicely done - although it's a shame in a way - everybody heads for the info before having the experience. That's part of the tourist thing.
I hope they get rid of those big pieces of litter called the Stonhenge / Callanish / Avebury visitor's centres one day