If you have a bracket followed by symbols, e.g.
some text)...... some text
...abc))>=def
when you double-click the symbols it also selects the bracket
I'm not convinced it's usually wanted to select the brackets as well and I think it's better if it didn't, so you can hit delete to remove the non-bracket symbols and if you want to remove some brackets as well you hit delete again (you are already on the key so that's easy) whereas if you don't want the brackets you can't auto select at all and have to do it all manually
In programming languages you are not going to have many symbols so it's not a problem to do it manually but in text works where lines of symbols such often appear such as lines of dots in OCR scans, it's very helpful to double-click and have the bracket not included.
David