Once you have a street bike with a top case (rear trunk) you won’t go back to not having one. Both my bikes have one, they are quick-release but they stay on >99% of the time. It’s also a great place to install extra brake lights.
Who cares what it looks like, you can’t see it or feel it while you’re riding, and it adds so much more convenience. Stopping while out riding, lock up your helmet and gear. Carry your lunch and briefcase to work. Bring a change of clothes/shoes or extra layers along with you. Stop by the grocery store on your way home from hitting the twisties. Heck, use the grocery store as an excuse to go for a ride.