I used to be very opposed to promos, and can totally understand where people are coming from.
As I played more on OCTGN I found more and more people using them, either because they found the game first online, or they play mostly online. Promos are a distinction that matters most if you often play with cardboard, and you don't want to try to keep separate books and metagames in your head.
Ironically, this is one area where playtesters are at a significant disadvantage: we get used to having to consider lots of unreleased spells, having multiple spellbooks that can only played under specific circumstances with specific people, and confronting cards with incorrect balance.
Because we play with unprinted stuff all the time, we are the worst people to ask about how players feel about promos.
Thank you for reminding me of what I once knew well.