I work with a lot of engineers, programmers, IT people and for some reason, many people in these groups tend to have slightly different social norms than the rest of society. Some are clearly on the autism spectrum, some may have social anxiety or similar, some are simply a bit "awkward" or "strange". This is definitely not something limited to the technical types I've specifically mentioned, but does seem to be more highly concentrated there in my experience. Nor does it apply to all of them!
So this means some people in the workplace often don't quite act in the socially "normal" or "expected" or "polite" ways. Some people find it hilarious, some people find it really awkward, others find it jarring or even rude.
Thankfully, perhaps because my own workplace is majority engineers/programmers/IT, this isn't an issue for managers/employees here. There may be the odd comment about how someone reacted a bit oddly etc, but there's a much higher threshold for what is considered "rude" or "bad manners" as far as simple social behaviours go, compared to a lot of other social situations. Even people who really struggle to work well with others have a place here, but that is probably more luck than attitude (since we have a lot of small projects, many which can be done solo).
So without knowing the individuals you're talking about, all I can say is maybe they don't conform to your idea of social norms, but that doesn't necessarily mean they're intending to be rude to you—they might just be a little socially "weird". And I don't mean that in a pejorative way at all (we're all a bit weird/etc), the only place it'd really be a problem is where the job specifically requires someone to conform with social norms (like a TV personality, someone dealing face to face with lots of clients, etc).
So if you don't know them very well, give them the benefit of the doubt; they might just not fit your model of how humans should interact socially, and it's not necessarily a sign of rudeness.
As a final point, it occurs to me I don't know if you and/or your colleagues are male/female/straight/gay/etc, so this can definitely add to any awkwardness—extroverts are often mistaken as flirting when they're just being friendly, and introverts are often mistaken as being rude/cold when they're just not feeling sociable.