Postpartum depression is not only something birthing parents experience. New fathers can go through a real depressive episode too, often shaped by sleep deprivation, a sudden loss of identity or freedom, financial pressure, or feeling like there is no room for your own struggle when your partner is also adjusting.
Therapy gives you a place to say the parts you might not say at home, that you are struggling to bond, that you miss your old life, or that you feel like you are failing at this. None of that makes you a bad father. It makes you someone going through a hard adjustment who could use support most people do not think to offer new dads.