Portable Power bank charging your phone or tablet should be simple

Portable Power bank charging your phone or tablet should be simple... but it's not. Most consumers do not have an engineering degree to make informed decisions on what type of charger they should get. People just want a charger and they want it to work. Why is it so darn complicated!?
Why are USB chargers so complicated?
It started out so simple... your old flip-phone needed to be plugged in to the USB on your computer to download photos or upload music. At the same time why not use that same computer port and cable to charge the battery in your phone? It made sense, saved money and simplified charging in multiple locations. All you needed was a PC, laptop or even one of those little wall chargers with a USB port. Anything would work. EASY!
So what happened? 
Well, the USB port in your computer has limited power output. Older phones had small batteries that did not require much for power so there was no issue. Then came the smartphone with heavier power requirements and larger batteries. The typical USB port would take an unacceptable amount of time to charge your new phone. More current was needed for faster charging and the PC USB port just wasn't good enough. A larger USB wall plug that can handle the power output could be used but that created a problem. Smartphones are smart in some ways... but not smart enough to know what they are plugged into. When you plugged your new phone into your old USB charger or PC it would max out the power output of the device. This could cause your charger to burn out, potentially even start a fire! On your PC the USB port could break unless it had fail safe cutoff in which case it would shut down right away and not charge your phone at all.