[Origin of the IDPA vest?]

I wonder the same, was IDPA founded by the paparazzi? I do wear a vest when the weather warrant but not for any actual concealment purposes (yes it does help but nor the main method). My guess would be as mentioned previously, safety reasons - and possibly for a consistent concealment method for scoring purposes.

[Can you get XLS files from Practiscore? Trying to do a point series]

You can copy/paste right from the practiscore results page into excel. I've had to do it a couple times when fighting to sync tablets. The data pastes fine, it just takes some manipulation with formulas to set up the ranking.