Maybe you've never had a project manager whose whims change with the wind, and interrupts the sprint to add yet another high priority bug in the middle that absolutely-needs-attention-right-fing-now... every sprint. Scrum tries to stop that.

Of course, if your project management listens to you and trusts you, you don't have this problem, so I understand your take.

Sounds like you've had an awesome career with no experience of people slamming unnecessary work into your workload, or trying to design in detail things that won't be implemented for 6 months, and will have been redesigned 5 times in that time. For everyone else, sprint backlog is a useful tool that you decide when you should violate it, and by exception only.

> Why would I do anything else

Because you'll get fired if you don't...?