I can think of four scenarios where this can happen:

#1 - You want weekends off, July 4th, etc and you intentionally bid reserve.

#2 - The person junior has vacation and bids vacation low - during the summer, you would have to get four four-day trips whereas they would only have to get two four-day trips. Unfortunately, the only way to fix this one would be to get rid of vacation low!

#3 - You have training and it conflicts with trips you could be assigned but the junior pilot has no conflicts. We currently only get 4 hours of credit per day of training meaning yearly recurrent is only worth 16 hours when you bid. This one honestly should have been negotiated to include the CBT credit (~4 hours) or with the option for a higher virtual credit.

#4 - Either you have a carry over pairing that causes conflicts or they have a carry over pairing that gives just enough credit. I honestly think there should be a union controlled over-ride on this one.