10s power in a race. 10s power + time when I'm training.

1. You remember the exact distances of decisive points? Oh wait.
2. You use distance to figure out when you should turn home instead of your NP/kJ on the ride so far and kJ to go and your ability to generate that kJ? Scrub.
3. Hint: there are speed limits.
4. Hint: you can estimate wind vector given grade information, power output, and typical/estimated speed at specific W output.

1. Yes? It's not that hard.
2. Being on a group ride is a scrub move to begin with.
3. No speed limits where I ride are low enough to be concerned about, along with most other people I'm assuming (military bases are the exception). How many speeding tickets do you think are issued to cyclists every year?
4. Why?

1. Liar.
2. Strawman. Just admit you're a hypocrite for using distance (which is a function of speed) instead of kJ (which is a function power).
3. A lot actually. People also perceive speed based largely on wind resistance, while your ability to corner is based on ground speed.
4. To get a general estimate how much incremental power you need to attack. Hammering at 15mph airspeed vs. 25mph airspeed is vastly different.

1. Nope. I can remember a couple of numbers. If the course has laps, I'm pretty good at multiplication as well. I'll admit that if I ever did Paris Roubaix, I'd have to do this.
2. I admit it's a little hypocritical for using distance, but not really. If I honestly had a kJ target for a day, I wouldn't be doing a group ride. Group rides for me are just about being social and aren't for real training. I could switch entertain the switch to kJ though. For road racing, I'll stick with distance.
3. I think our definition of 'a lot' differs. I would also bet that anyone who was going fast enough to get a ticket on a bike would also know that they were speeding without a speedometer. Also, are you seriously suggesting that you should look at your speedometer while you're descending? Put your attention on the road where it should be so you don't crash. Racing cars don't have speedometers, they can handle cornering without it.
4. I don't know a single person that would actually try and do that math. I think it's pretty easy to tell if I had a tailwind or a headwind.

Let me ask you something. I assume you have a powermeter. Do you actually take any action based on your instantaneous speed or do you just like being pedantic on the internet?

1. Liar.
2. kJ is absolutely superior for racing. NP-adjusted kJ is even better. Miles are not all the same.
3. Yes, you should take a look. Another strawman, because car racetracks aren't even remotely analogous.
4. You don't need to do the math to understand that you shouldn't attack into a headwind. I don't think your mental wind gauge is as calibrated as you think. Human perception sucks.

Yes, I do. More relevant information has minimal detriment. In fact, because information display on my Garmin has nearly zero cost, there's no reason to not have speed.