Yes, you do. About 15 percent of people over 18 have some hearing loss and you can’t predict who by age alone.
If you don’t use a microphone, you risk losing a part of your audience from the first word. That’s assuming you speak loud enough to be heard by people with normal hearing. That’s not always a safe assumption, depending on the environment or your speaking voice.
Don’t ask, “Do we really need this microphone?” That forces people with hearing loss to identify themselves. Instead, step up to the mike. There’s no downside to making yourself more easily heard.