At North Weald, run and breaks are no longer permitted on certain days (eg Saturdays when the market is in operation on the eastern side of the main runway).
Run and breaks are not always done "purely for fun and effect". For example, with a formation of aircraft - and there is a lot of formation flying done in Yaks as well as other civilian aircraft - a run and break to join is quite simply the safest way of taking the formation and getting all of the formation aircraft on the ground quickly.
The alternative is to break the formation up away from the airfield and then have multiple aircraft joining - a much longer process with those aircraft then creating a very busy sky - eg 7 individual aircraft joining in rapid succession.
Naturally, when bringing a formation into the circuit, the leader must be cognisant of all the other circuit traffic, (no difference from any circuit joining there), and it is usually to the benefit of all other traffic for the formation to enter the circuit as a single identifiable unit and then to get on the ground and out of everyone's way as soon as possible. I think one would usually find that aircraft performing a run and break will where possible fly a tight brief circuit to land rather than a "cross-country" circuit perhaps forcing other faster traffic to fly a non-optimal circuit at low power etc etc - itself a practice which has its dangers but which you can find at any given airport on any given day).
Obviously, one needs to time a circuit entry differently when leading a formation as opposed to being a single aircraft - if the circuit is crowded, you won't find large formations wandering in and breaking to land regardless of other traffic - common sense really.
There is a strong case, certainly in my opinion, for run and break procedures to be flown at airfields that will permit it. I agree though that it would be helpful for airfields that permit the procedure to write it up for the enefit of those many other pilots for whom the procedure is otherwise a mystery.