Reasons why coatings and/or seal might not be the best approach:
-No concealing (not every finish can be corrected well enough for the coating, or a sealant, to look OK)
-Difficulties regarding spot-correction (including the need to relayer with multiple-coat-type sealants such as KSG)
-Subjective factors (appearance, beading vs. sheeting, scent, slickness, etc.)
-Time/effort/cost/requisite application skill
Note that I'm no coating-hater, I use one on certain wheels. I'm no sealant-hater, I use one (FK1000P) on most of my vehicles. But I can't do any more correction on the '85 Jag (not *bad* for single stage of its age) or the '93 Audi (simply awful condition due to original owner and its dark blue that shows every flaw) so those need concealing, and most sealants don't look right *in my eyes* on those cars anyhow.
Hey, give me a sealant that conceals and gives depth/jetting on dark colors and I'll use it on that Audi. Give me one that conceals and looks right on older single stage and I'll use it on the Jag. Give me an Accumulator-proof coating that's as easy to use as my current stuff, conceals marring, looks "right for the vehicle" in my eyes, and allows for easy spot-correction and I'd probably use it on everything ifit offered advantages over FK1000P. But I don't see any of my current LSPs as being deficient in any way for their applicatons, so why would I change? What am I missing by not using a coating instead of FK1000P? What am I missing by using a wax instead of a sealant on the vehicles that get that? Hey, those are serious Qs, give me some reasons! I might not change, but I'd enjoy discussing it.