Google Webmaster Tool and Backlinks

In GWMT I see links pointing at my site, but by inspecting them, nearly all are NOFOLLOW links.
I expected only "valid" links to be considered by G.
The links are about 3-4 years old (2009), so I can think that they once were "valid" and now they might be nofollow...but in this case why do they still show up in GWMT?
Is it not updated "regularly"?
If I search with the link: command, I get 0 results, although some of the links are actually "valid".

Maybe I'm missing something..

Can someone clarify?

P.S. "valid" used instead of you know what.

Checking your links profile on GWMT is not the best idea. The results are long way back and messy.

If you want in-depth analytics of your links, then try MajesticSEO.