They are very different programs. In a lot of countries they don't separate the genders for Scouting. Again, as someone who was a Scout and had their childhood shaped by the program, I see no reason to deny that opportunity to young women.
That's interesting. Again, I empathize with those that feel they are losing a "male only space," but that really isn't the case if you stick with the program and get really involved. There have been female adult leaders for a while. Venturing allows girls/women. I worked summer camp staff with multiple women, etc.
As I stated above, the opportunities offered by the program outweigh the value of keeping it a boys club, which isn't part of Scouting's core mission.
EDIT: The current idea of making separate packs seems like a short term compromise to me. The BSA has made a lot of changes in recent history and I just don't see that lasting. It'll eventually be co-ed all the way.