It's far too much trouble to wire up an NPN inverter for every single Led. Also, newer Leds
don't need anywhere near 20 mA to get good output, more like 4-5 mA on many. If you're
worried about current drive off the I/O pins, just buy some high-output Leds.
I've heard over and over that this is not the right way to do it and I can understand why.
Duh. The only thing right about the right way is don't exceed the current source/sink rating
for the I/O pins.