Just imagine buying a $250 VGC and forget using it. There are tons of unintentional human or system errors that can cause you to forget about a purchase, and that’s why I always tried to keep a log of all gift cards I have bought/used. I also keep a log of all hotel refunds after cancellations.
This is certainly time-consuming. At some point it might become too much but right now I’m still enjoying doing this points/miles/cashback game.