Because most of their complete series releases recently have been entirely done as combo packs, and I utterly refuse to buy those bloated pieces of crap. I should have to make my own coverart just to get a decent size case to hold the series in. Same thing with stuff like Shana Season 1 and Spice & Wolf. At least with their old sets like Samurai 7 and Full Metal Panic I could easily switch the cases out to ones that hold more discs.
EDIT: In better news, Iron-Blooded Orphans is indeed coming to Toonami later this year.
I don't follow. These complete series offer an order of magnitude more value. I almost always wait for the single complete collection versus having to buy a number of individual collections or seasons / parts at the same price or more each. Plus, I hate having all the extra boxes. I'd even prefer to buy all digital only, but the Blu-ray complete sets are often cheaper, more so when Amazon, Funimation, or Rightstuf has a sale.