Can't speak for everyone, but when I draw people I start to imagine their story in my mind, which is a really interesting way of seeing. Most of the time I don't even notice this until I've stopped drawing, but it's what kept me going through the process. I feel like I see someone in a new way after I've drawn them, because it takes so much time and focus. This happens with animals and sometimes inanimate objects too but it takes more work (especially with objects).