A very large group of gamers are min/maxers, which is not something you can do in Seasonal. Not enough time. Not all of us want to abandon our build every 2-3 months and start over. If I were wrong, and Eternal was as dead as everyone claims it is, Blizzard would not have bothered offering the same Battle Pass to us on Eternal. They did that because Eternal actually has a pretty significant player base.