happytreesi think it's because they don't know how many you need because of different formats.... 50 is fine for limited, and 2x 50 is fine for edh and non-edh formats, not to mention these are not magic specific sleeves, magic cards are one of the main standard card sizes so it also fits most other card games and board games that fit cards...
TL;DR - ultrapro is screwed no matter how many sleeves they put in a pack, it's the wrong amount for most people
edit - what i am upset about is that they want $13 for 2 packs of ultrapro sleeves ($2.5-$3 each at LGS) and 2 polyurethane deck boxes ($1/give away/can't get rid of them) i have literally tried to give away deck boxes like this when i was cleaning out magic accessories, and no one wanted them (even with good art)
edit - what i am upset about is that they want $13 for 2 packs of ultrapro sleeves ($2.5-$3 each at LGS) and 2 polyurethane deck boxes ($1/give away/can't get rid of them) i have literally tried to give away deck boxes like this when i was cleaning out magic accessories, and no one wanted them (even with good art)