I think it boils down to how horrible the driver R-Pro is, since that was the first iteration that most people tried. Putter and mid blends are totally different. I mostly have experience with the R-Pro Aviar (or in my case the P-P1) which is just simply totally bulletproof. You can't break it, it has no structure to speak of so it can't be broken. It's a bit less stable than a new DX Aviar P&A, but still very usable, even for drives if you dial in your hyzerflips.
It also just happens that the best iteration of the best disc ever made was the first run P-MD2, featuring a stiffer R-Pro than the putter blend, but waaaaayyy more durable than the driver blends and still insanely grippy. It's not premium tough, but it beats DX in durability any day, and resists gouging and small cuts better than regular Pro. I've also tried R-Pro Rocs that look totally trashed and still fly great on slightly understable lines. I hear that the RW-Pros were insanely brittle though.
The feel of the discs on the other hand definitely isn't for everyone. That's a matter of preference, not an inherent flaw in the plastic.