USB 2.0 ports can be connected to USB 2.0 drives at normal speeds

If you are transferring large data, a faster transfer speed of USB 3.0 is appropriate, and a cheaper 2.0 would be fine if you are transferring just the usual small Documents files.]

Another point is Power Management.

Compared to USB 2.0, USB 3.0 provides more efficient power management.

USB 2.0 supports up to 500 mA, while USB 3.0 supports up to 900 mA.

[As a result, the power supply is up to 2.5 W to 4.5 W (at 5 V), so USB 3.0 can charge faster than USB 3.0 and USB 2.0 ports.]

Finally, USB 2.0 and USB 3.0 are compatible.

USB 3.0 ports and USB 3.0 devices are backward compatible.

USB 2.0 ports can be connected to USB 2.0 drives at normal speeds.

It also works when connecting USB 3.0 drives to USB 2.0 ports.

[However, when connecting USB 3.0 drives to USB 2.0 ports, 3.0 USB 3.0 does not receive the normal speed transfer rate]