Now I like git but I can totally see why people don't use it (or in fact any DVCS). The central repository model is easily understood and implemented. The idea that there is no central "source of truth" is confusing--possibly even alarming--to an outsider.
Windows support problems for Git go beyond having no TortoiseSVN equivalent though. When I was setting this up I at first tried to get Git over SSH working with PuTTY and it a hair-pulling out experience. I eventually abandoned that effort in favour of Cygwin, which just worked.
Also Git's CR/LF issues on Windows are a pain. The fact that I've never seen an issue with them on any other SCCS, and they seem to cause headaches with Git is another reason it'll have trouble catching on in a big way.
TortoiseHg for Mercurial, on the other hand, is a pleasure to work with, especially the 2.0 release that just came out.