Weights and calorie output.

I would like to know why there is no calorie out put for doing weights on the exercise section here?

I do a lot of weights (I also do a fair bit of cardio, but I am concentrating on weights at the moment) and when I put in my weights it does not register a calorie output. Now I am far from an expert, but surely there is a way to estimate a calorie output for doing a weights session.

Why you may ask? Well, as we know, if you build muscle you burn more calories throughout the day (which would be difficult to calculate). So encouraging people to do weights is beneficial to them when they are trying to lose weight (dress size or a measurement is better). If they cannot see that they are burning calories doing this, they may not try weights and they will be missing out on some of the best fat burning workouts they can get.

Now obviously it would be different for different muscle groups and intensity, but if it was made as a generic calorie count for the different exercises or even muscle groups it could add to your end result.
Example (obviously not accurate calories):
If you do a good chest session for 40mins you may expend 300 calories,
or doing legs for 60mins you may expend 450 calories,
biceps and triceps for 60mins may be 200 calories.

You could even calculate it by weight, reps and sets to make it more accurate, for instance:
1 rep of squats at 100kg = 2 calories x 10 reps = 20 calories x 3 sets = 60 cal.
Calf raises 10 reps at 60kg, 10 calories x 3 sets = 30 cal.
and so on.

I am sure there are some smart people out there that could figure this out.