As I understand, the basic concept of Session Hijacking is intercepting a packet in which the victim sends its cookie/session credentials to a server, be it Facebook/Twitter/YouTube/Whatever.
But wherever I look and whatever I read, a MITM (Man In The Middle) attack is required. And I do not understand why. Packets are broadcast to the entire network. I can see (or at least should see) those packets with Wireshark regardless. Given that if I enter with my laptop in a coffee shop, I should see all traffic on that network, why do I have to perform a MITM attack?