I don't understand what you've understood…
Parentheses need to be paired for the outer literal array to be recognized.
Technically, opening parentheses could become elements, but not closing parentheses, since then there would be nothing to close the literal array. And it would be strange to read if you could have several ((( but only one ) at the end.
Instead, pairs of parentheses enclose an array, which is nice because it makes it possible to have literal arrays as elements inside literal arrays. If you want a single parenthesis as an element, you have to explicitly write is using the symbol syntax.