In case of business or jobs?
I've studied it half way using Petzold

Win32 API is when you intend to develop Windows specific applications. Most likely those desktop Windows software we have seen. If it is Web-based, I think they are promoting .NET services instead. If it is mobile-based, I they are promoting their Windows Mobile SDK instead.

So depending on the company business model, if they are into Web-based on mobile-based then I would think Win32 API may not be immediately applicable.

We developers have to go with the times. Win32 API used to be 'hot' skill-set back in the 80's and 90's but with the dawn of Internet, the focus changed to Web-based. Then now with the dawn of mobile, the focus changed to mobile-based.

Im a hobbyist.......adn find it fun to understand the basics of how Windows work

Windows API is the base of all windows technologies, it all builds on top of it. Learning it to understand what is going on under the hood is anoble undertaking.

Thanx..
Ex. I lyk 2 knw hw time is recorded(trapped)
How device size is known by the PC etc.........