Good thing it doesn't hurt when it ends abruptly. Bad thing, its absolute needlessness. Humans are social animals. Social interaction plays an important role in everyday life for most—for those that live within a society, at least. But, why should it matter so much when we all know, after it ends, it didn't matter that much?
It gets smaller, as we talk; we talk, as it gets smaller. It will end, we usually think—and know—, it always ends, but it can surely become heavy while it lasts. It should be light, shouldn't it? You talk about nothing (nothing important, anyway) and it gets smaller and shallower. Something small that grows smaller should also grow lighter, but it doesn't—it grows heavier and harder.
Awkward silence is what happens when two or more people that don't know each other well—or at all—keep their mouths shut in a situation where they should be knowing each other; in a situation where it's too late to choose not to know someone—you say "hi" or throw a smile—starting by the shallower layer (usually the weather). Why is social silence so awkward? Because in society we're talking machines, probably; because society wasn't build upon silence, perhaps; because our culture demands an active role, maybe. Silence can hardly be active. So we talk, we small talk.
Try this, just for fun. When confronted with a small-talk situation, break the rules; talk about the most tragic or private event that has ever happened to you. This should instantly lead to either (a) awkward silence or (b) a true conversation. You already know what to do with (a): talk about the weather. It's my opinion that people should only talk to each other when they have important things to say, though I must admit that most big things in the world start being small (like a tropical rain that grows into a hurricane, talking about the weather).
Discrete things are awkward, so even nature fills in the gaps between discrete things with that we call "emptiness" to form a continuum. No, we can't see the air surrounding the beginning-and-end objects we can see, but sure we know it's there while we breath it. No, we can't speak the silence surrounding the beginning-and-end conversations we have, but sure we know it's there when it gives us time to remember about the week's weather.
It's my opinion that social silence should not be awkward, but it's a … lovely weather, isn't it?