Honestly a second look is designed to give an applicant perspective into the every day action within the residency program (i.e. volume, teaching, interactions, support).
Just like a thank you (interest) letter or note, its mentioned in rank sessions and will help the applicant. But not having done one doesn't hurt the applicant as programs are adults (so you hope) and understand the financial and time sacrifice it takes from a medical student to arrange a second look during the interview season.
In my personal experience, all the second lookers liked our program & vice versa it helped their application. The only instance I recall the exposure to a candidate hurting them was when this one student did a sub-I and basically turned out not to fit in with the group at all.
Hope this helps ya! Good luck!
