One word replies show laziness and a lack of give-a-damn, in many cases, but they aren't spam.
I will say nothing infuriates me more than when I am texting someone and attempting to get answers out of them, and they constantly give me the "k", or "sure" type answers. It makes me feel like they have no interest in even conversing with me. And maybe that's the case, but it literally took me less than a minute to type this. So..yeah....laziness. lol