Because there's a threshold of where youknowhow things will be parsed. You wouldn't write:
a=(b+c)
Because you know it's not necessary. But we're human and sometimes make mistakes when we're sure we didn't.That's also why we allow for some misunderstanding, (rather than (writing (using) (sentence trees))).
I'll never understand why programmers don't simply put parens where theywantthe expression to be evaluated, rather than relying on their (sometimes incorrect) assumption about operator precedence. I want to chalk this up to hubris, but it's probably just laziness.