Because Mac OS doesn't straddle the worlds perfectly well. It's definitely more compatible than Windows/Cygwin, but you still spend a lot of time trying to get things to work and/or compile correctly on OS X that would work effectively "out of the box" on a Linux machine. A recent hire has insisted on using a Mac OS workstation and his install time for new tech stacks is through the roof when compared to developers on Linux workstations.
Yes, that has been my experience. Most tech stacks I use install better under Linux. Even if I were using a Mac as the host OS, I will still run Linux as a VM.
