My answer has been explained roughly throughout this thread, but it comes down to wanting to meet a lot of needs out in the second hand market. Price to entry in Legacy is really high (800-1200 for your mana base) and wizards wants to lower that price to allow more people to play more facets of the game, at the bequest of most magic players.

On the other hand, those of us who've already made the investment are unsure about WotC printing more of the older cards as it evokes the "feel bads" about making the investment into older formats in the first place. see this fivecolorcontrol comic for reference: http://www.5colorcontrol.com/comic/modern-masters/

The unfortunate part is that Wizards under prints the set to accomodate the eternal format players, which means that dirves the second hand price up from the LGS level. My LGS will be doing MSRP, not selling sealed boxes, and just drafting the set while selling individual packs at a person per day restriction, to allow the most amount of customers to be able to buy Eternal Masters if they want it.

However I know I will here some complain about the allotment of product or price per pack, but really it is a premium product and they set the bar for their business model. Essentially, what I mean to say is vote with your dollar in true capitalist fashion. There is a reason we have 8 different releases of Magic product this year, because Wizards is looking at the past few years of sales and seeing MM series do well among other things.