It's important to remember that factory-made clothes are not that old as a thing. And it's only been a few generations where nearly all clothing is expected to be factory-made (even though most factories are still humans quickly pumping out items), let alone carry brand names on them like you're a nascar.

And thinking of clothing as akin to open source software is fair. Before the industrial revolution, all clothing was hand-made, almost entirely at home or by a friend, or a tailor if you had money. From the end of the 18th century until pretty much the 1980s, sewing patterns were the paper version of open source software. Could be copied infinitely, forked and changed, traded and borrowed, or created from scratch if you knew what you were doing. Magazines included them to boost sales, just like how software magazines used to include pages of code you could try at home - no license needed.

Fabric stores were commonplace for a century or more, and big box stores reserved a huge amount of floor space for fabric sales up through the 90s. Patterns were trivially inexpensive, and picking your favorite material for the pattern was how you could personalize it.