My thinking here is that most people who are wanting to keep normal brakes haven't ridden a mountain bike, or are people that recently got into mountain biking and have only known the power of discs.
I've raced MTB's with cantilever, v-brakes, and hydraulic discs. In all conditions, from rainy all day epics in mountains to dry flat terrain. The brakes have gotten better and more powerful in the order I listed them. I still think that if it's dry and you are in flat terrain that doesn't require a lot of slowing down, v-brakes are fine on a MTB. As soon as it rains, yes, they still work, but hydraulic discs are A LOT better. And this is at the 50-40 km/h max you hit on MTB trails. I can only imagine how nice they would be on a wet road ride/race when you are at 80+ km/h. If you think it can be fixed with better technique you obviously haven't ridden/raced in the rain. Lower power is lower power, you can't stop as fast. Good technique is being able to slow down quickly, and in as little distance as possible for a corner to maximize the time you spend at a higher speed before the corner. If discs allow you to slow down to the required speed faster, then you will be at a higher speed for longer, and therefore, faster overall.
One road ride I did was particularly frightening and made me really want discs that day. It was in South Carolina, we did about 180 km that day and it was pouring the whole time, and we were in the mountains the whole time. It was training, so I had open pro's and standard Shimano pads (Ultegra), not known for their poor power. They were brand new at the start of the camp down there, and this was the 3rd day in, practically no wear. By the end everyone in my group had little-to-no pads left, quite a few were metal on metal. Only 'technique' that would have kept us safe is being pussies and not riding, but hey, coach said ride. Point: my MTB pads last half a season in all conditions, don't wear out in one ride (unless using organics in a wet sandy race, but that's another story).
Do we NEED them? No. But they will make the ride a little nicer, and probably a little faster. That's called development. Of course there will still be the hardcore WW's that will keep the rim brakes.
Of course there will still be the hardcore WW's that will keep the rim brakes
I find it kinda funny because there are also threads here about which road brake is more powerful and how many people won't use certain lightweight brands because they don't give enough power.
OK, well I've raced road for the last 20 years, cyclocross for 8 and more recently mtb's for the last 5 years in ALL conditions from the 8 day Cape Epic to 24hr muddy races in the UK. Discs have their place, without a doubt in MTB and I'm glad to see the UCI allow them in cross as well. Road riding in mountains in the wet can be scary I agree, but even in the wet on the road I'm more concerned with sliding than braking and too much power can be a bad thing! You dont have abs on a disc brake! You can easily lock the back wheel with the brakes now, so why do we need more power unless you can also get improved traction on the road!Agree that because of the crossover from cyclocross we are no doubt going to see more discs on road bikes but the compatibility issues will be ridiculous.
BTW, disc pads can wear rapidly as well. MTB in Wales on a wet day and you can go through a set of pads in one ride. Its wonderful when you're halfway into your mtb ride and hear metal on metal and realise your back brake is out of pads. Havent had that happen on a road ride yet.... All pads wear, it just depends on the conditions......