Crossovers are expensive

This whole Newsarama article here tells just how much it could cost to buy all the books related to this summer's crossovers (via The Beat). And even if it's just either the main miniseries or some of the connecting books, it's still very costly, and no way to draw in newcomers.

Eventually, no matter how they're structured and advertised, these crossovers are going to become far too costly and interfering with other storylines for people to handle. And that's why the time has come to retire them.