I think some people are naturally frugal. I always go out of my way to save money on business trips even when there's no benefit to doing so, and no drawback to spending the money.

I'll take Uber pools, walk, or take public transit even though I'm technically no restriction on my transportation spending. Likewise, unless I'm taking my team out to dinner, I'll usually grab a $10 gyro or something instead of going to a nice restaurant.