why google pr is not update in 2013?

[Peter Nikolow]

Well GooglePR isn't updated - you're right. Before few years they have updated PR on regular 3 month basis. The problem is that Google is changing - Panda, Penguins, EMD, Hummingbird, keywords not provided, etc. This mean PR little bit outdated and irrelevant to SEO. Also one more thing - PR is just number but can't explain niche of this page. Just imagine if you are in insurance business with site PR3 and you purchase link from site with PR7 but with military equipment. In this case higher PR will not give link juice to your page, even can hurt it! Because both pages are irrelevant as content.

Second - there are 2 PRs. One is Toolbar PR that you're talking about, second is PR used only from Google but it's hidden and we can't see it. IF you want to see true PR you can use Moz OpenSiteExplorer and see DA/PA - they are almost equal as PR. You can use this as prediction did PR will be up or down on next update.