I am an adult (45) and I can do many things that other adults do like changing the brake pads on my truck, change the oil, put together tv stands, assemble BBQ grill etc but I can't psychologically take on the task of tearing down a fishing reel to clean it.
IMHO, my reasons are easy for me to understand. I took apart my first baitcaster, a Shimano Bantam Mag Plus 250SG, when I was 12 or 13 and try as hard as I could, I couldn't get it back together. I didn't even remove C Clips or anything like that. I just took the handle side side plate off and I specifically remember the little springs giving me a lot of trouble. My dad refused to help me get it back together. My mom took me uptown and I paid a guy at a tackle shop $9.00 to put it back together.
I think that incident scarred me for life! LOL