Various ponds are dry and/or unrestored for various reasons
Management for wildlife and / or amenity
Situation; Ponds which have good access for the public are given greater priority by the various funding bodies.
Construction - cracked concrete - though there are thoughts to line an existing concrete one with clay and see what can be achieved.
Cost and Practicality
Some sites have been built on or are now unsuitable for a wildlife project.
The funds available are to restore, not experiment.