When working properly, it can tell you when things are not quite right. If you had a suction side blockage, the PSI would drop from the normal level. If you had a return side blockage, the PSI would rise from the normal level. I think it is one of those things that is nice to have but probably not necessary.

Usually, people will clean their cartridges when the PSI raises by 5-8 PSI so I am a bit surprised at the 30 PSI comment. That would mean you run at 22 PSI normally.

I oversized my filter by so much that I don't see much of a PSI rise. I just clean my filters at least once a year and maybe twice.