Here is the setting that makes the YouTube app suck...
Yes, make this video available on mobile phones and TV. Note, the video may not be available on all devices due to copyright or licensing issues.
Just clicking this setting DOES NOT mean the video will be available to the APP, if ANY possible copyright issues are present, YouTube defaults to NOT showing it or allowing it to show up in mobile search results even.
I could see this changing for tablets over time (if it hasn't already) but last time I played with an iPad, this KILLED the functionality of the app.
So either A) you are missing out on a ton of content or B)the APP and YouTube policy have caught up and made changes since December.