Pikies are travellers or gypsies.
We had a covenant slapped on us too, by our own family. So if we develop any part of the farm, they will reap the benefits .....they already are reaping them with the payout. It is quite usual nowadays for people to cover their backs, so to speak.
Really, if you intend to only use the land for agricultrual purposes, and keep it that way, then it will not be a problem.
I suppose if you put the boot on the other foot, and consider if you were the seller, did not put a clause on, and then a year down the line, found the buyer had made a packet on putting houses on it. Their solicitor will have said they should safeguard themselves against this happening.