When you perform in a band and want to quickly change songs, you don't have time to transpose in this way, so you need the registrations be already transposed... There was a time in my country when the changing between songs without a little pause (about 3-5 seconds) was not pleased by audience... Now times changes, and we (bands) "taught them in wrong way" and now they are not pleased if there is a little pause in our performance... So we have to perform songs as medleys, which means registrations I have to store them already transposed...
But, everybody does how it is used to...
We have to choose what is better for us, easy in the same time, low consumption time, etc... a lot of factors...
Regards,
Vali