A Stark, Dried-Up Piece of Land with a Mound in the Middle of Nowhere
Imagine Tatooine minus its inhabitants and cool sand architecture and you get the gist of what the setting of Happy Days looks like. The stark and desolate setting serves to remind us that, ultimately, the world is a random, chaotic, and cruel environment; absurdism at its finest. In the Theater of the Absurd, the overarching thought is that life is meaningless and purposeless—think back to the incessant and random ringing of the bell. In fact, we never learn why Winnie is in the situation she's in, nor are we supposed to. Ultimately, it's kind of beside the point.
In fact, since he never explains why Winnie is buried, Beckett's script begs audiences to identify with Winnie, to see parallels between our lives and her experience being stuck in the mound: we didn't ask to be born; we didn't choose to be in this world, but hey, here we are, just like Winnie. The question Beckett poses is, what do we do now that we're stuck here?
It's pretty clear by now that Beckett had a thing for simplicity and stark, post-apocalyptic settings. The play's setting tells us that this is humankind—stuck, stripped down, raw, and (like Willie) naked. In other words, this is what the human condition looks like minus all the gadgets, routines, and stuff that we use to fill our empty days.
If you haven't noticed by now, Beckett was pretty pessimistic.
And yet, Winnie continues. She persists. She knows that her situation is difficult and yet she knows that "the show must go on," regardless of what our setting looks like.