I've noticed the last two marvel sets haven't had the collectors boxes. Anyone know why.

WizKids decided to stop making collector boxes, starters, playmats and dice bags with each set. As to why, your guess is as good as mine I suppose...

We still get the occasional Starter Set as a stand-alone item. The drawback though is that, since the dice are only found in that starter, you have to buy 2 of them to get the maximum amount of dice for each card. The same goes for the Team Packs they put out.

I feel like it may have something to do with dice masters not selling very well in certain areas. Which means lack of support. I stopped actively following the game when they started making the sr cards really hard to play. Having to have 1 of every energy type really put me off to playing that card. Especially sense most teams i built ran only one to two types I'd never go above two.
Prehapse other players felt the same.

Simply different marketing methods.