That is because SKILL is really an scheme under the hood. And somebody had the bright idea of making the syntax more "user friendly" (read: more like C) by inventing a rule that "foo(bar)" parses as "(foo bar)" while "foo (bar)" parses as "foo (bar)". IIRC there also is another similar rule for when expression is parsed as infix.

Right bracket with the meaning of close all was used in some lisps because somebody did not like the long runs of closing parens at the end of definitions.