Starting a campaign with the party meeting each other in a tavern and getting an adventure hook there is a bit cliche, I admit. But sometimes it really is hard to come up with a back story that involves all party members, especially if the players get a bit creative with their builds.
How else do you explain the pious ascetic monk, drunken kobold pirate, dragonborn wolf cavalier, dwarven feybound warlock, and a starborn golem empath adventuring together?
Randomly sitting in a tavern together as someone bursts into the door looking for adventurers is about as good an explanation as any when it comes to a group like that.