Jerry Seinfeld famously said that supporting your favorite team is really just cheering for laundry. Back in the early days of professional sports, uniforms were a very loose concept. Old team photos show in the black and white graininess a group of stone faced average joes with glorious mustaches (only seen these days on a penny farthing in Portland) all wearing vaguely the same color long sleeved sweater, some with turtlenecks, some with initials of the team awkwardly seen the the front, some completely plain.
Team shirts eventually became more important, firstly for the game officials to keep track of players, but also as an identity for the team itself.