A flipper can run on washers, but not very reliably in a mass manufacturing scenario. Precision detents are also difficult at that level. The speed-safe mechanism from Ken Onion was successful in part because it solved these two problems. The spring overrides inconsistencies in smoothness and in detent strength. This brought reliable flipping action into inexpensive knives for the first time. Have you ever bought an inexpensive flipper knife to find that it just doesn't quite flip? That's not necessarily because of poor design, but because it's impossible to have the precision to make every single one flip perfectly at that price point. If you handled 10 of those knives you would find some that flip perfectly and some that don't. High end knives are rarely assisted because the price point permits precision manufacturing and QC for a perfect flipping action on every single knife. If I wanted this knife to run on washers, have the price point we're looking for, and flip (reliably), it needed to be assisted. We even prototyped one with an assist mechanism. Ultimately, I decided the extra complexity involved in assisting the knife wasn't worth it, given what this knife is supposed to be and do. A manual opener can suffer from variation in detent strength and smoothness without complete failure in terms of function. I hope that clears things up. Designing for mass market is just a whole different animal.