As an American, I'm constantly confused by this when watching UK television.
I would call the [ a "bracket", and only if I had to clarify would I say "square bracket" to distinguish it from a curly brace { (which is sometimes called a curly bracket) and I don't think most Americans would even consider a ( a type of bracket at all.
If I had to come up with a rationale, I would say that physical brackets are almost always more square than round, and a bracket graphic in the sense of a sports bracket is also usually square, so brackets are square!
I asked "which dialect of English calls parentheses 'brackets'", but apparently I got it backwards, and it's only US English which makes the distinction!
I actually prefer the US usage, as "parenthesis" is such a lovely metonym that describes the thing it encloses.
People are used to indicating so anyway in speech (referring to a parenthetical remark). And while in writing parentheses can acceptably be set off in a variety of ways, I have a fondness for the good old parenthetical brackets.
> Curious: in which branch of English dialect are parentheses called "brackets"?
Quoting Wikipedia:
> In most English-speaking countries, an unqualified word "bracket" refers to the parenthesis (round bracket); in the United States, the square bracket.
> What makes the technique useless for your reading/browsing experience?
It is entirely a matter of personal preference; I tend to read very quickly, and long complex sentences laden with parentheticals are more enjoyable than obstacular.
I would call the [ a "bracket", and only if I had to clarify would I say "square bracket" to distinguish it from a curly brace { (which is sometimes called a curly bracket) and I don't think most Americans would even consider a ( a type of bracket at all.
If I had to come up with a rationale, I would say that physical brackets are almost always more square than round, and a bracket graphic in the sense of a sports bracket is also usually square, so brackets are square!