Because these two are just so randomly adorable.
Ode
There's something about Xander. Something about the way he walks and talks and… there's just something about him. He fixes things around the house right after a demon attacks, then fixes it again when it happens two days later. He doesn't complain about the job, because h loves it. He loves working with his hands.
And he's always making jokes, no matter how bleak things look. Even when the jokes are lame and not funny (or only funny if you're a huge geek). Without even trying, he always finds a way to lighten the mood. He doesn't hesitate to poke fun at himself, and when he lost his eye, he treated it like ti was no big deal. Even made jokes about that too (though the one about the party in his eye socket should never be repeated).
And he's human. Totally and completely human, which was kind of refreshing in a house full of slayers and potentials and witches and keys (though the concept was still hard to grasp) and ex-demons and vampires. Sure, Giles was human, but it wasn't the same because he was a watcher and kind of old. Xander was different. He was so human, so normal, so powerful, even though he didn't have an ounce of mystical power in him.
And yet, he still fought alongside them. He could have left them long ago, because he wasn't anything special, he didn't have powers that made him useful. But he still kept fighting, because he didn't abandon his friends.
And he was a total geek sometimes. He made references that no one got and said things that didn't make sense and he was just a geek and it was kind of adorable.
There was a lot about Xander that made him special, that made him different.
There were a lot of things that made Andrew love him.
