Is crying necessarily a good thing? Why is it? (I'm genuinely curious.)

I have a sense, based only on my incomplete understanding of how my T ticks, that she would find it uncomfortable if I were to cry in session. Maybe I'm just projecting what I would be feeling, though. Other mental health professionals I've seen have had a box of tissues somewhere around (one %&#€"#€"&& woman even told me two minutes after I sat down the first and only time I went to see her that "there are tissues if you need to cry" which to me felt very much like an intrusion). Current T doesn't have any tissues in her room that I've seen, and I've taken that as a hint that tears aren't welcome. Again, I may be completely wrong in my interpretation.