the original post did say he put his phone in the saddle bag and yes I have seen people put food in the bag. if you don't think you can feel the difference of a saddle bag on your seat, just try taking your bag off and try some sprint passes. I'm talking about standing and rocking the bike in the big ring. okay, if you have a heavy brooks saddle, you might not really notice a big difference, but if you have lightweight ti rail flite saddle, why would you strap 300 grams on it.

remember, the saddle is like a lever and you're pivoting from where the tires meets the ground. now if compare 300 grams to 600 grams at the end of that lever.