Re: why isn't USB 3 more widely used?
The other reason is that few applications actually NEED the transfer speed of USB3.
Technically, you can plug your mouse or SD-card reader into a USB3 port, but it will make 0 difference on transfer speed as the bottleneck is not the USB2 port.
Storage benefits from USB3 and future webcams will take advantage of the faster transfer speed to output RAW 1080p video for example..
As the universe is curved, there cannot be a straight answer...