My old man has been playing for 30 years, if not more. It just naturally passed on to me when he got me my first when I was 11. 12 years later, I'm still playing, I've owned more guitars than fingers on my hands, and still love playing everyday (which I do usually play half-an-hour every day, or at least I try to!).
To speak to why? IDK, I guess it ran in the family. I'm not an artsy person. I have short stubby "workman's" fingers/hands instead of musician's fingers so I'm at a genetic disadvantage. I generally don't like loud noises due to some of my autism. Yet I've stuck with it. I think the reason I end up sticking with it is because I can see music as "numbers" and I kinda want to prove to people that music is math, not feeling. It's also something that I've invested so much time and effort and energy in now, it would shameful to quit... it's actually a real skill I have that I enjoy. I have played for people before (most being about 50) and it's too stressful IMO, but people enjoy it and think I'm "good" or whatever.
From an objective point, piano is way better. The skills are more transferable, the instrument is more universal, and it is far easier to learn music theory and related concepts. Guitar is terrible at naturally teaching these things.