If you’re at a lure party, it’s easy to not have time to transfer stuff or if you’re considering something that’s ~80% IVs.
There’s also times where I swear I’ve transferred something only to have my pokemon box fill up (andI had 700 space at the time).

Is it more efficient to generate power by making an Electabuzz run on a wheel, or just making them zap some kind of rechargeable battery system?

Seriously, where did you think “Pokémon candy” even came from?

Personally I refer to the transfer machine as “the Woodchipper”