Is it Rude to Ask Someone About Their Disability?

I have Congenital Hydrocephalus. and I'm not afraid to say it because I'm not ashamed of it. Saying that, I went through Disability/SSI and I went to college with my favorite girl ever Maple, my Service Dog. She was two when I got her. She was a Golden Retriever. She got to go everywhere with me. The beach, she got to go actually ON the rides at Disney World, into restaurants, she even went to college with me! We were inseparable. People in college said her name first THEN my name. For example instead of Jake and Maple people said Maple and Jake. haha Because she was the only dog on campus. Yeah, you can say we were pretty well known around campus. My point of this is is it rude or illegal to ask someone their disability? Shouldn't you already tell if they have a disability if someone has a service animal? I mean many, MANY people asked me on campus what my disability was because I don't "look" like I have any. That's because all my disabilities are pretty much to do with my brain. But I am off balance a bit. That's why I have Maple for support. She's actually quite small for a Golden Retriever, according to what her trainer told me, she's only 60 lbs. But the way she braces is very strong 💪. So, I'm just wondering if other people get asked if they have disabilities and if so how do you take it? Are you offended? Or do you think they are truly just curious?