
I haven't seen an "official" explanation from Marvel. This (along with a review for issue #73) is addressed in the video below.
We know that "Old Man Logan" hasn't been coming out on a consistent schedule. Issue #73 is a good "jumping on point" since it's the beginning of an arc. Could the reason be that Marvel wanted to release another new Wolverine comic while "X-Men Origins: Wolverine" is still playing in theaters? Is Marvel more concerned with gaining new fans rather than worry about those already reading the comic? Won't there be confusion for those new readers when they pick up 73 and then see 72 in a couple weeks?
What do you think about the fact that this issue was split into two parts rather than focus on one story? Do you feel it was misleading to have an Adam Kubert cover and not have an entire Adam Kubert cover?
