I think there is some truth in this, at the risk of generalising.
I think that the ratio of professional/hobbyist differs between commercial and OSS operating systems: Windows tends towards professional and OSS tend towards hobbyists, not sure about Mac.
(before the knee-jerk replis come in, I know there are professional OSS users out there, it's the ratios I talking about).
Why does Windows have more professionals? I think that a lot of companies don't trust things that are cheap/free. I heard from an old boss a story of a trip to a software/hardware conference for a specific vertical market: a new vendor wasn't getting any
interest in his cheap product, after taking advice he multiplied the price by 10, suddenly potential customers started to take him seriously. It's weird, but it seems to be true.
I think that professionals tend to view their software as a tool to get the job done, while hobbyists take it as a religion. The different in professional/hobbyist ratios shows in the 'culture' of the specific software.
There are zealot on both sides and calm professionals on both sides, it's just that the balances are different.