A quick user needs exercise on why offices might still be required...

I'll start.

As an employee I need safe and adequate space in which to work.

As an employee I need safe and adequate space to work with other people where that work required close physical proximity to one another.

As an employee I need to provide an environment that can give me and my organisation credibility when dealing with clients, suppliers and potential new hires.

As an employee I need access to physical resources that are too expensive/cumbersome/risky for me to have at my own home.

As an employee I need a secure space where I can work on confidential things that are too risky for me to work on at my own home.

As a manager I need to be able to onboard and train new starters. (from @SmileyKylie74)

As an employee I have need to create a level of mess to enable creative thought processes.

(this one will totally fall foul of rigorous clear desk policies that will become the norm).