I don't know why - but being a directional school just seems to be a step down from being a school with a name.
Obviously it's four year now compared to 2 year then. And I understand wanting to take advantage of the BYU brand - so I'm ok with the name change. I just think it loses some prestige (can't think of a better word) by being "BYU Idaho". And I'm not sure how much it has to do with Idaho.