Introspection

When I'm not sure whether or not we have coffee plans, why don't I call you and ask? Why do I show up, just in case, considering the possibility of being alone better than the possibility of standing you up? Simple communication could prevent both situations. Why do I do this?

Delving deeper, I find several reasons:

- I don't really mind it that much if you don't come. I don't mind spending the time alone, and I usually have something I enjoy to occupy me. Not that I'm okay with being stood up - that's not the situation here at all. If I suspect that you don't think that we have plans, it doesn't hurt my feelings to find out I'm right. I can usually see what would lead you to think that, even if I have support for thinking otherwise.

- I don't want to make you feel bad. I'm sure you're content in your assumption that we do not have plans. I'm sure you don't realize that I consider the situation more ambiguous, and I don't want you to feel guilty for not coming.

- I don't want to make you feel obligated to spend time with me. If I call to verify that we have plans, I am suggesting that I think we do. If you think we don't, I have created an awkward situation with our difference of interpretation. Your options are less than ideal: you can either come and hang out with me, counter to your expectations, or you can turn me down and cancel our "plans." I would rather hear nothing than "no."
My reasoning here lies on an assumption that could be faulty: that sudden plans with me are a hassle rather than a joy. Maybe I'm wrong. Maybe you wished we had plans though you think we don't; maybe you would love a call suggesting a coffee date that to you seems last minute. Maybe you're feeling lonely, and my intrusion would be appreciated rather than resented.
Why do I assume the opposite? Because that's how I feel about people sometimes, so it is more than fair if people think that about me...

- It's kind of embarrassing to see something where others do not and to assume that a certain exchange means that we are getting together when that's not what it meant to you. It makes me look desperate, so I'd rather keep it hidden and uncommunicated, even if that means I end up sitting in the coffee shop alone. Ironically, that makes me seem way more desperate than simply calling you to confirm - but at least you don't see it.