Older sites don't really need them. Especially these larger companies. IMDB has been in the business for over 10 years. The site was launched in 1990. These older sites are usually owned by larger corporations, therefore the amount of advertising dollars they spend each month brings them these unique visitors into the site. After they've reached the PR10 level, I don't think they need to accomplish that goal of newer sites trying to push PR levels up and up.
Newer sites need to do whatever they need to do in order to succeed. MW3Blog for example didn't have all that much traffic until the months before MW3 was about to release to retailers worldwide. When I bought it, it was barely even picking up 5 visitors per day. Barely.
CODForums on the other hand suffered almost the same fate and it was on vB4 with vBSEO installed. However, when I transferred CODForums to xenForo, which is a product that Kier made. The site changed ranks.
I was expecting google to index the site slowly, but instead, the site started to
grow, and then when I posted that
Kick Mule Cola thread. The thread grabbed the keyword of the thread title ...Word for Word on the keyphrase "Mule Kick Perk-A-Cola" and then a few other variations of that keyphrase. Barely half a day, the site starts getting busy, and I'm asking myself "WTF! What did I do?" I post it to facebook and twitter that afternoon, the site starts to explode like a ticking time bomb.
Then MW3 came out, a few days later, the server went offline. Imagine that.