The SEM Insights blog discusses four reasons why big brands don't have good SEO. They are:
Requirement: ease of maintenance: Therefore, they may not be using CMSes that are SEO friendly.
Requirement: personalization and tracking: They need quantifiable results, but they don't understand that search results are going to display the most applicable page to a search query and that that every related page probably won't rank in the top 10 for a search.
Requirement: language: Big brands often serve content to different countries under a single TLD. The problem is that when people in different companies search for in-country results, they won't locate the big brand.
Corporate policy and legal issues: The last thing is that it takes forever in big brands to get things done. To put it simply, there's way too much bureaucracy in the corporate world.
At Sphinn, the discussion continues. Forum members believe that sometimes they'll take the easy sale (an ad representative with a solid presentation) and ignore SEO (especially since they have the money to afford PPC).
Another thought is that they're just so used to doing what they're doing that change is difficult. Indeed, the IT department makes things difficult. Their mantra: "if it ain't broke, don't fix it."
Additionally, some copywriting just sucks. Some people just won't use keyword-rich text because they want to sound more professional and that prevails over search friendliness.
What big brands need is a shift in thinking. Unfortunately, they need to kick it off if they're serious about it.
Forum discussion continues at Sphinn.