three parts to this answer:
1. i like big dicks. i really like seeing holes stretch and people struggling to wrap their hands around em.
2. they're really fun to draw. floppy, hard, droopy, semis, vascular, smooth, just lots of stuff u can explore when there's a bit more surface area.
3. size correlating to libido is a fun idea/dynamic to play around. spoke to o11 about this years ago but i like to view hyper sizes in art as a representation of hypersexuality - even though i know they are not the same thing. and subverting that dynamic can also be interesting.

of course i also like smaller dicks and i also like drawing them! i just don't really do it much because i never put focus on the ideas i have that include them. i'm not a fan of shrinkage or micropenis because it just makes me feel bad. i think if someone has a small penis it should be appreciated. big dick humiliation is really enjoyable.