It's one thing to meet a celebrity you love in a passing moment, it's another thing to win a date or hang out with them where you get one-on-one time with them (and their full team of security).
Oftentimes, contests where people win dates with celebrities give proceeds to charity, or function as a PR stunt to help promote the famous person's newest project. Regardless of the purpose, it can still be a fun opportunity for a fan to connect with someone they look up to - and potentially learn a bit more about what they're really like.
Ray D'Arcy hosted pretty much the only kids TV here in Ireland when I was growing up. Thing is I grew up close to the border with Northern Ireland and watched BBC instead of RTE so I had no idea who he was.
So I won a writing competition when I was like 9, school principal drove me like 3 hours to a big event with loads of people and I was sent up on stage to get one of those giant checks for the school. After that the guy presenting the check came and sat at our table and I just couldn't understand why everyone was making such a fuss about this regular looking, strange man. I was even more confused when he signed my school journal and handed it back to me