The reason that is there is to protect people from issues that may cause the unit itself not to perform to it's full potential (or get harmed)...and also keep the support calls to a minimum. By far and away the most of the time we build harnesses for the units, but occasionally people are installing units into panels where they are updating another unit, already have some of the wiring run, already have a bunch of the wiring done, or are hooking it to other stuff that is already wired and in that case many times the owner will do his own interconnect wiring.
The devices will always be under warranty if purchased from an authorized dealer, but it depends on what/where the warranty is handled. If you purchase a pre made harness then PSE will fully support the unit directly with no questions asked because they already know the harness was built to certain standards they require and therefore their support technicians will likely not have to spend time troubleshooting certain aspects of issues. If the harness was not built by one of the shops to their standards (or by the builder), then the warranty is normally handled directly by the company who sold it - which is why dealers are pretty picky about who works on those units....no fun getting stuck covering warranty on a unit because someone accidentally put a power wire into a ground pin.
Rest assured the PSE products are top of the pyramid for many reasons including their desire for quality installations. In many regards audio stuff is almost black magic...so if things are not always followed fairly closely the unit and it's superb characteristics that they are known for may not perform at it's full potential (or worse)! Also note that by a large margin audio wiring is one of the most critical parts of the panel. Anyone venturing into building their own harness should fully know all of the implications of doing so because a little variation from standards can cause a big problem.
That's my take on it!
Cheers,
Stein
I also forgot to mention that sometimes it's not their choice and you can thank the FAA for some of it. For mfgr's who are producing certified units in a certified facility or repairing them in said certified facility they have to adhere strictly to a set of prescribed and documentd procedures which cannot be altered even slightly no matter if the unit is certified or experimental. Note that mfgrs of experimental equipment have much more freedom than the guys making certified stuff (Garmin, Bendix, PSE, lycoming, Hartzell, etc.) are all in similar situations and beholden to various rules....Another example of the Fed's helping hand!
