Have you previously annoyed them in some way, or had a disagreement?
Were they in the middle of a proper conversation and might’ve felt like you butted in with a greeting?
It sounds odd. I’d have a think about whether you’ve previously annoyed them in some way, but if not then they might just be grumpy. In which case there’s nothing to worry about, and you just do you.
I don’t understand how people don’t indicate in general. It’s just so automatic for me, I’d need to make a conscious effort not to.
Sometimes I accidentally indicate because I’m going around a sharp bend that my brain registers as a corner 😂