Why use a booster/topper? Dunno, but perhaps…
1. The elements that provide the durability and chemical/environmental protection of a base coating do not provide/are not compatible with the more entertaining aspects folks associate with a ‘good’ LSP.
Things like slickness, exciting water behavior, beading, added gloss. In other words, the base coating provides the functional aspects, the booster the aesthetic aspects. Gyeon Mohs, Gtechniq CSL for example are some pretty tough customers but the visible water behavior is visually not that entertaining (especially after they age a bit), hence the Skin topcoat in the Mohs-based Syncro kit and the ‘preferred’ CSL +EXOV4 application combo.
On their own, Mohs and CSL are more hydrophillic as opposed to hydrophobic and that’s just not as visually entertaining as when topped with a more hydrophobic top layer. While Skin and EXO are ‘kinda coatings’ like CarPro Gliss, Feynlab Topcoat and TAC Topcoat, the concept of topping a coating via dedicated ‘topcoat’ or booster is, to me, kinda the same. The base coating, for whatever reason, can’t encompass all characteristics people recognize as ‘quality’ behavior of an LSP.
2. Sacrificial layer or protecting the protection. Better to contaminate a top layer than the more expensive base coating.
3. Revenue generation. More products needed to maintain the base coating benefits, real or perceived. “You spent all this money on getting it coated, what’s a little bit more?” Kinda akin to changing oil every 3500 miles instead of following mfg recommendations of up to 10k intervals. Better safe than sorry?
4. Just following directions. Most mfgs recommend some kinda maintenance topper, necessity of it being irrelevant. Again, better safe than sorry?
There’s plenty of well-respected coating aficionados who coat and let it ride…with excellent results so topping is definitely not necessary in all cases. May as well throw ‘personal preference’ on the list as well.
I dunno, really…interesting topic but at the end of the day, gotta do what works best *for you*. If that involves toppers/boosters then so be it. If not, no harm, no foul. Variety is the spice of life.
As for myself, I enjoy using them so a lot of it for me is pure entertainment. Now that I've finally settled on 'my' coating, one that works best for my specific needs, wants, climate and vehicle usage patterns there ain't much entertainment involved aside from washing (which I find to be a chore); sometimes I think I wash an otherwise 'acceptably clean' car just so I can squirt some other stuff on it. It's easy, quick and I *think* it makes a difference in appearance in water behavior but lacking proper instrumentation, who really knows....but I like doing it.
Once thing I have noticed regarding the relationship of coatings and toppers is that toppers seem to become less effective (longevity and overall performance) as the base coating ages. I first thought "Eh, I can extend the life (or apparent life) of the coating by just topping it more frequently as it (the coating) loses it's 'goodness'" but it doesn't seem to be a linear situation. :shrug: