From what I've read the MacBook can output 15W on a port, so I'd expect a hub to be able to output 15W when one device is plugged in, 10W+5W with two, etc.
Consider for instance the new 14" and 16" MacBook pros: They got rid of the 4th Thunderbolt port in favor of an HDMI port, likely because of internal bandwith constraints. They could have kept Thunderbolt and HDMI, and only have one Thunderbolt port on the right side work when HDMI is plugged in, but they didn't, because having your external drive work only when your monitor is unplugged is unintuitive.
also, I've found that no one obeys the current limit for inrush so now your downstream ports have to allow 7.5+W until they enumerate and you can lower the current limit.
additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires?
> additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires?
If they don't know device power levels they can just learn what can simultaneously go on a single port when they try, like with USB 2.