Probably because he/she likes his/her linux gadgets, and sees the choice of Nokia for Windows limiting the linux phone options in the future.

The problems Nokia has are numerous. They choose a radical option with windows, betting that it would solve the problems in the future.
Based on the demand for the current Lumia phones, i would say it probably put Nokia in a worse position (at least for 2012).
If they continued the Symbian/MeeGo course Nokia would also have huge problems. Sales would have slipped (probably not as much as with Lumia, but still), and they would have needed to develop all the software on their own.
Look at all the features in iOS6, I don't think Nokia could have matched those in their own operating systems in any competitive timeframe. Will Microsoft be able to do that? I doubt it, but we will see when the Windows 8, Windows Phone 8 and Windows RT arrive.