Have you considered people can enjoy different things than you? I personally enjoy a nice exhaust tone and I like subwoofers as well. And I don't like them just because they might piss off somebody like yourself, it's for my own enjoyment. Not all exhausts and subwoofers are created equal. Most modern cars with 'premium' sound systems like Bose, JBL, etc. have subwoofers, but they're usually small and don't require a lot of power. The system they installed in this car might have been the OEM premium sound package as well - the one Toyota offers is JBL and comes with a subwoofer. Do you get mad when it's OEM or just DIY? The GR Corolla has a 'loud' exhaust from the factory as well. Loud enough that you'd probably rage at it judging by this comment.

People buy aftermarket exhausts for a variety of reasons. They can produce a different tone, cut down on exhaust 'drone' (which the GR Corolla is notorious for with it's factory exhaust), offer alternative styling, provide weight savings, and reduce backpressure/improve flow. It's not just about volume. Certainly you could be an asshole who buys an exhaust just because it's loud, but that's not why the majority are doing it, it's for their own enjoyment and usually provides a performance improvement. If they really wanted to achieve max volume they could just do an open dump exhaust or a hood exit, it would be cheaper than buying a Borla and significantly louder.