Brushing is important not just to remove tangles (as in long hair) but also to help remove shedding hairs. It's a nice time for you and your dog to spend together, and most dogs enjoy it.
Yes you have to brush him regularly. But don't ask me whether I am doing it regularly or not because my boxer won't allow me to brush it regularly. My boxer is very naughty so it was not possible for me to does brushing regularly.
I use a "Zoom Groom" on Keeps when his shedding is bad. It costs less than $10 and really gets the excess hair off. I also use it to massage in shampoo during baths.