1. If you are using a tube-style device (as opposed to an assisted-locking device) and if you do multipitch climbing, with the attendant possibility of falls with fall factor greater than 1, then you are at risk for severe burns if you don't wear gloves. This has been tested over and over again and is part of the design features of ATC's: the rope will run in high fall-factor falls when there is low system friction.
Now lots of folks are going to reply that they have been climbing since the dawn of time and have caught numerous "giant whippers" and never had the rope run. This is because severe falls are extremely rare, requiring both high fall factor (the faller falls past the belayer) and low friction in the system, and so people conclude, incorrectly, that the the rope can never run through the device. It can, and your hands and possibly your partner's well-being are at risk if you aren't wearing gloves and a bad fall happens. This is an example when "experience" isn't the best thing to go on, at least not if you want to be prepared for the worst scenarios rather than just the average ones.
2. People's grip strength is at least somewhat correlated with body weight. A 100 lb thirteen year old girl may climb circles around a 200 lb guy, in the process seeming to be much stronger. But her hands only have to hold her body weight, and he is double it, putting her in a very vulnerable position when it comes to catching him. So gloves for the lightweight partner become increasingly important as the weight mismatch between partners increases.
3. Sadly, gloves will decrease grip strength. Tests suggest 20-25%. This makes it more likely that the rope will run in a big fall (but remember tube style devices are designed to do that), but also more likely that the belayer will manage to control the rope without injury.
4. I think almost all belay devices claim ridiculous rope ranges. Handling for the larger sizes is bad, and friction for the smaller sizes is inadequate. The middle third of the claimed range is probably the only range with decent handling and friction. If you are using skinny ropes below the middle third of your device's claimed range, it is even more likely that you won't be able to hold a big fall without a lot of slippage.
5. The dynamics of catching a big fall do not seem to me to be widely understood. There are two phases, each involving the rope slipping through the device. In the first phase, the rope slips through the device and pulls the brake hand towards the device. The rope does not slip through the brake hand during this phase, and fall energy is absorbed by the rope running through the device under tension from the brake hand. In the second phase, the brake hand essentially hits the device and, if enough fall energy has not been absorbed, the rope continues to slip through the device and the brake hand.
So, the rope burns and possible loss of control occur in Phase II. It follows that one should want to get as much Phase I action as possible. This means having the brake hand as far as possible from the device at the instant of braking, allowing for the largest possible amount of rope to pull through the device and contribute to fall energy absorbtion before the brake hand hits the device.
I have no valid survey information, but the belayer behavior I see is often as ineffective as possible from the point of view of Phase I enhancement. The majority of the belayers I see have their brake hand almost touching the device, which means that in a severe fall they'll be in Phase II immediately with the rope smoking through their hands with no Phase I benefits. Compounding what might be viewed as bad belaying technique by not wearing gloves is signing up for the worst possible results if something really bad happens.
Here's an analogy to think about. More and more people are wearing helmets to at least mitigate head injuries. I've worn them since they became as light and ventilated as bike helmets, but also climbed a long time without them. That said, I've never had any incident that required a helmet, nor have most of the people I know. If we used "experience" as the guide, we wouldn't wear helmets. We wear them in spite of what "experience" tells us, because we understand that they protect against rare but potentially devastating events.
I'd put gloves in a similar category. The reason they aren't there for most climbers is that hand burns aren't the same as a head injury, and we hear a lot less about hand burns as well, precisely because they are not generally as devastating. Lindseth -- 6/5/2014