Some unsubstantiated numbers are being thrown around. It's always better to do your own homework.

I'll state numbers that Futaba uses.

S-Bus is designed to handle 10 amps using Futaba supplied SBus components.
This includes hubs, extensions, decoders, receivers. If powerboxes and other items were necessary they would be part of the Futaba product list.

Remember all the arguments against dual batteries? We remember the days when miniature turbines in models were considered really cool but impractical. All the "experts" on compuserve were convinced of all the disastrous reasons they weren't safe, and would never be used by the average modeler... It's always tempting to spend money on gadgets to stuff in a jet, but don't add complexity based on rumor or inaccurate fear-mongering.

Sbus is designed to simplify, not add to the box count. Maybe it's not for every application. No system is.