For a long time, people didn’t think too much about the pronouns they used when referring to certain individuals. But the more we learned about gender identity, and the more we listened to the community most impacted by misuse of gender pronouns, the more we realized that pronouns actually matter.
The main reason is actually pretty simple — using the pronoun someone prefers, whether that means she/her, he/him, or they/them, is a show of respect. But that’s not to say that it doesn’t take some practice — it does, and that’s okay. If you aren’t used to referring to someone by their desired pronouns when they don’t match up with the idea you had of that person, or if someone you know recently transitioned, you’re bound to make mistakes.
The important thing is to listen and to make sure your intentions are in the right place. Refusing to call someone by the pronouns they most associate themselves with, though, is another story altogether. It shows that you aren’t willing to adapt to make someone else feel seen, or feel comfortable.
Source : https://www.littlethings.com/why-gender-pronouns-matter/