Part of the reason: Tribes and other alternative frontends. Can't blame it all on the content producers. Can't create your own brand if all you do is follow trends either. It's great to have content that drives eyes here, and to the ads. To keep those eyes around, variety matters.
Search "constiposted." Search "NoNamesLeftToUse" even, click the images tab on Google, majority of the top image hits are my work. There's actually quite a few strange queries that would lead directly to me, but now they don't always lead to Steemit, whereas before other frontends became popular, all these little roads I made led here to Steemit. So I suppose it's worth mentioning even if people do everything they possibly can to drive eyes here, there's still a chance the hit will lead to another frontend.
I noticed that issue a while ago. If google sees the other website as the "better option" it might even hide the Steemit URL version of it or at the very least it could be very deep down in the search results.
Over the long run I expect one of the tribes I use to over take my Steemit pages if they keeps growing and my content keeps performing well there.
That's cool we need as many roads as possible that lead to Steem! Keep laying down the "breadcrumbs".