Why is electron flow taught in some contexts?
Current flows out the positive lead of a power supply and back in thru the negative one.  We have arbitrarily decided that electrons have negative charge, so electrons actually flow out the negative lead and back into the power supply via the positive lead.  Electrons being negative is a convention, but a universal one.

Current doesn't have to be soley from electrons flowing.  It can be due to charged ions physically moving in a solution, for example.  In that case, the positively charged ion really do travel in the same direction as what we call the overall current.  Of course, negatively charged ions flow the opposite way.

If anyone teaches this differently, they are just plain wrong and doing their students a gross disservice.

However, from the electronics point of view, we don't really deal with individual charges moving.  We think in terms of current, and all works out, whether that current is realized by negatively charged particles moving in the opposite direction or not.