Pzh.2000 and Caesars are simply rare, and on top of that were many times noted as very buggy&maintenance-intensive - so only a few were hit (but huge percentage-vise, compared to the number of vehicles destroyed).What we've seen destroyed is mostly the shorter range stuff, highly mobile systems such as pzh2000, Caesar etc have been rarely seen as destroyed.
The one modern /52 SPH deployed in visible numbers by Ukraine - Krab - is a reasonably frequent visitor of lancet footage.
The simple answer is that it's exactly on the move when they are often getting spotted, tracked down to their new fire location - and engaged.It'd be interesting to see each side's analysis on why these systems are getting destroyed.
These are mobile systems that should be backing off after their fire mission. They should be hard to locate. Unless of course, they keep coming back to the same exact spot every time.