I am not sure why you feel so. Despite different people writing them, most often they are influenced by the keywords in the title or h1 of the page they link to. This is more natural.
I disagree. If you look at a reasonably large site, that hasn't engaged in any link building campaigns, you'll nearly see "Brand" being the number 1 anchor text. You'll also find "brand.com" ranking pretty highly on top anchor texts too.
Some kind souls will of course link to you with the target keyword, but these will be few and far between, which is what you must mimic, when you're link building.
If even 50% linked with the keyword, it's too much IMO. I've always felt this way, long before Penguin.