Why am I making an OS?
Once upon a time I had a Commodore 64. For programming I only really had 2 choices - write assembly or write BASIC. BASIC was an interpreted thing (slower than a dead snail) so I learnt 6502 assembly.
Later (still a long time ago), I decided to shift from the Commodore 64 to a fancy "PC compatible". I was used to a system with 64 KiB of RAM and a simple 8-bit CPU running at about 1 MHz; and upgraded to a system with 128 times as much RAM and over 100 times as much processing power (80486SX at 66 MHz). With such a massive increase in hardware capabilities (and price) I was expecting to be amazed at how awesome the software would be. Welcome to the world of the future! Um, no sorry, it's DOS. What a massive disappointment that was.

So, what does an assembly language programmer do with very powerful hardware and an incredibly disappointing OS? I started learning 80x86 assembly, and started writing an OS. This was before anyone I knew had Internet access though; and getting adequate information was a major pain. That changed later.
First came Windows 95 - the OS that was 5 years too late. Then came the Internet (and networking in general). My plans changed from "realmode OS with decent GUI" to "protected mode distributed OS with decent GUI".
As time passed, hardware got more powerful and software got more complex. New file formats were introduced, languages were invented, Unicode and internationalisation came, an army of web developers rose up. The world I was used to (where it was easy to write software) became a place of confusion with 500 different (and incompatible) ways of doing "Hello world". Everything turned to crap.
My plans have changed from "protected mode distributed OS with decent GUI" to "redesign and replace all the crap". It's not really an OS project anymore - the OS is just the most obvious place to start.
Cheers,
Brendan