I find it weird that when measuring height in metric, people using cm exclusively, i’ve noticed this a lot actually, people will use cm or mm in places where it arguably doesn’t make any sense. I could see the justification for doing math maybe, but like, that defeats the whole point of it being metric no?

Why is that defeating the whole point of being metric? If you know someone is 183 cm tall, you also know that they are 1.83 m tall. If its easier to say the length in cm, you do. No need for "one meter and eighty-three centimeters" or "one point eighty-three meters", just "a hundred and eighty-three centimeters". Often you just skip saying the "centimeters" part as well, because most people can see that you're not the size of a skyscraper without getting a ruler out.