We recently came across a website (not ours) that looked very plain. Not just aesthetically but even on the back-end. Now, I’m just a novice compared to Supasmo and ChrisB but even I can tell when a site doesn’t have the basics.
For example, no analytics. Not just Google Analytics but no trace of any analytic. 
(Super frowny face!) Personally, I don’t know how you have a website without something on there telling you where your visitors are coming from, how long they’re staying on the site, etc. Fascinating.
Second was the absence of meta stuff (tags, title, etc). Don’t get me wrong, adding meta stuff will not propel your site to the first page of Google overnight but it does help. As Wikipedia says:
Meta elements provide information about a given Web page, most often to help search engines categorize them correctly.
If it’s free to use and doesn’t take a rocket scientist to accomplish, there’s really no excuse.
