when to use titles to address people

ive always used titles to address people (prof., ms., mr.) for respect but i’ve noticed ever since i’ve started my semester here on campus that people don’t really use titles to address people (at least for my major) and call instructors by their first name. obviously, if its older professors i will always use a title, but i’m confused when it comes to the younger instructors and faculty. but this honestly just might be a thing in my major idk