The logic, as I understand it, is to give a carrot to down-and-out teams while also promoting divisional rivalries and intra-division competition. Win your division and you will get a home playoff game, period. It has been a simple message.
Does it become unfair when a second-place 12-4 team must travel to play an first-place 8-8 team? Yes, that seems unfair. But is also makes winning your division a more important criteria than amassing a great record, and that 12-4 team failed to win its division.
Personally I would change the rule and have the team with the best record be the higher seed, but I think the owners are strongly opposed to a change.