You know, much it might have been just a lot of poor planning. As stupid as it would be, maybe they hadn't even thought up making the COMPLETE SINGLES collection until late; and since she had just released an album, she's at the beginning of a whole new cycle. She can't produce an album that fast, so we can only get singles (musically speaking).
Maybe she isn't producing as many live appearances and magazine shoots as many of us would like, but there could be so many reasons for this. They could be as simple as she's too lazy at the moment to something like she simply has not had enough time in between touring (despite what many of us may think). She just may be too tired for all we know.
And heck, we do have a whole half a year left. Her touring will be done, and maybe that's what she's waiting for. Maybe she just wanted to focus on her touring first and then go promotion crazy. Maybe she's not even sure herself what she'll do after the touring (she is a 'live for the day' sort of person), so they can't really promote much. And who knows, maybe (doubtful, but let's go with it) she'll throw a whole album at us without giving us any singles as a surprise!

That wouldn't probably be a good idea, but who knows!
Either way, bottom line for me, I'm sad there hasn't been more so far, but I understand she's got other things to do at the moment and she's got lots of time left to wow us.

Hopefully she doesn't disappoint.
Edit: what if this whole time she was disappointing everyone on purpose and actually has a grand plan to wow us later?