Not necessarily. Sometimes people think too highly of themselves and their own thinking, and if others aren't they (in all their "highness" ) approve of they presume that their thinking is the one and only gold standard.
Also, some people pretty much get into a habit of criticizing "as conversation". I've known people who seem only to have their opinions about one thing or another as conversation material.
Some people who view themselves as "knowing better" and/or as "above" someone else (like a spouse or a grown child or a parent) criticize out of seeing "flaws" in that other person.
Some people may have even learned "the rule" in, say, school or work, that one should be able to accept constructive criticism from a teacher or supervisor; but then those same people see themselves as "teacher" or "supervisor" to others in their personal life (maybe a friend, maybe a spouse, may a son or daughter, whoever). In other words, people learn that "rule" within the context of being a student in school but lack the "human skills" or general "well adjustedness" to know enough to separate the context within which they think criticism is appropriate.
Also, if someone expects another person to say what he wants/needs them to say (maybe because someone wants the other person to make him feel better about something, or maybe because the person has built up something about his own "identity" in his own mind; and when the other person says/does something that "shakes" what he's created in his mind but what is not real; it can become a matter of "It's you or me". If it's something that matters very much to that "critic" he's more likely to do the "...you or me" thing.
People also criticize when they judge others without knowing what others are going through (or worse, without even thinking that others exist beyond just what the critic sees/knows.
Some people seem to just be in the habit of criticizing. Maybe their mother didn't tell teach them well enough.
Some people actually thinking that they're "trying to help" by trying to help others measure up to their self-defined "gold standard" of what people should be/do.
There's also the "mean-girls" type of behavior that can involve some people getting together to "dump on" someone else; and therefore boost the egos/sense of self-rightousness/superiority of all in the group.
Then, too, there are critics who are just clueless in general and don't know how clueless they are before criticizing.