Question scanners and USB hubs?

[DLes]

I'm using a Canon LIDE120 scanner with an iMac 10.11. Every once in a while, the system would report that the scanner was not connected. I jiggle cables, etc., and can't get rid of that error. Finally, I cycle power, and everything is fine. Very annoying. Turns out, this scanner was connected via a powered USB hub. I connected it directly to the port on the machine, and the problems seemed to go away. In fact, if you do a little online research, you see that one of the main suggestions in scanner connection problem-solving is to remove any USB hubs from the communication channel. Now, duh, whyever should that be? I think of a hub as just a pretty transparent relay connection. Why should a hub actually screw up connectivity? This post isn't really about solving a problem, which I think I've accomplished, but just trying to understand the solution.

 

[rgd1101]

cheap hub? does it have power saving?

 

[DLes]

It's just a simple Monoprice powered hub. Works fine for other things. Does appear to be made in China. What is "power saving", and what might that have to do with the problem? The very brief instructions for the hub don't say anything about "power saving".

 

[DLes]

So, no ideas about why hubs don't get along with scanners?

Epson, Canon, and many others, suggest that a hub might not be a good idea. Just wondering what they're thinking.
https://epson.com/faq/SPT_E10000XL-PH~faq-52032?faq_cat=faq-topFaqs

Canon Knowledge Base - Common Problems and Solutions (P-215)

support.usa.canon.com