Simply because I was always the skinny kid.
No matter how hard I trained when I was younger, no matter how much weight gainer I consumed, I was still skinny as hell.(so I started taking Goshin-Jitsu) Then when I turned 25ish it all slowed down and I started making gains(and I loved it). Then a couple injuries....and I got fat, now, I want to shred the fat and get huge.