Well, as you are saying, the fact that an overwhelming majority of the owners will never take their cars to the track probably has something to do with the lack of a brake fluid sensor/reading. Pad temperature sensors might be a different deal though. Designing a sensing mechanism that will work realiably at high temps into a part that is meant to be changed often when used heavily might have some serious cost/benefit limitations. I guess they could have a non-contact temp sensor mounted on the calipers facing the rotor to pick up rotor surface temps, but I don't know how much such a system would cost. I guess there could also be liability issues when you introduce a safety feature that is not common place and expected. Why take the risk given most people won't need it. Does anyone know how exactly they measure brake temps in F1? I'm pretty sure they are doing that in real-time.
About the stock pads not performing well at the track. I think that is justified in the sense that they do need to make trade-offs between cold/hot performance, and noise expectations, not to mention cost, for determining the stock pad specs, and that obviously cannot be biased toward track use. I heard that the track pads BMW sells in Europe and Canada cost $1500. Your average owner would be outraged at that type of expense during brake service if that was the stock part despite the fact that they would cost less if they were indeed to become stock equipment. And they are supposed to be noisy as hell (remember the press reports from Spain when BMW called them over to a track there and all of the cars had track pads).