Saying 'Can I let you know nearer the time?' when issued a social invitation.
My OH does this, but what's worse, does it through me.
I'll look up from my phone and say, "Janet and John have invited us over next Sunday. Sound good?"
"Oh, I dunno. Can you say we'll get back to them?"
"Why? Have we got anything on next Sunday?"
"Well, that's it. We don't know what's happening next weekend."
"Er...this. This is what's happening next weekend. So do you want to go, and if not, why not?"
"Look they don't need to know right away. Tell them we'll get back to them in a day or two."
"That doesn't help, does it?"
"Well, they're your friends. Just fucking go if you want. Jesus - why is it always me that has to make the decisions?"
....and so the long summer evenings just fly by.