Condominium ownership required specific legal authorization in the U.S., which only happened mid 20th century. Before that there was no way to have different people owning different units in a larger building. The closest thing to it was a cooperative, in which you also don't really own your unit as real estate, although it isn't quite the same thing as a UK leasehold, it overlaps.

So, the UK didn't even pass similar legislation to legalize a condoninium-like ownership structure ("commonhold") until the 21st century. And it's still not quite the same. And for whatever reasons hasn't taken off much, maybe because the leasehold system was already so developed at that point. Switching over ownership structures in existing properties is of course a big hassle (why are there so many more cooperatives than condominiums in NYC, even decades after condos were legally authorized? that's part of it)

So, people do it, because that's what evolved from the particular historical and political context to allow "ownership" of an apartment in a building. There's noting "natural" about condominiums, they needed specific legislation to make them possible in the USA too.

In the context of council estates specifically, well there's a bunch more historical and political context. Land ownership and tenure is a social and political construct, it isn't "naturally" any particular way, it turns out.