It's pretty important, actually - unless you're also running Medium (and have, like, two Cybersolutions out or something ), you're probably not doing both Keyhole and regular runs. Thus, you don't really have a good idea about when a Jackson is coming - they could have one in hand at any time. Even if you can count three trashed Jacksons, they could still be running Archived Memories and/or Interns, etc. That's why you want to be snatching Agendas as soon as it's convenient - it just adds to the pressure, because now I don't have to get into Archives to win, and Jackson might not help you - I could pull a random one from HQ, I could snatch one from a remote, I could Maker's Eye for one, etc.
Sure, there's cases where you just straight out need to steal all the agendas in one fell swoop (Iain, The Source, NACH, that kind of thing), but that's mostly full-on Keyhole-dedicated deck we're talking. If Keyhole is just one of your tools and you just want to get to 7 by the most convenient means necessary, don't marry yourself to the glory run, it's an unnecessary weakness that can potentially be exploited.
Or, think about it this way: if you don't ICE archives properly, I can go get the agendas from there as soon as they total 7, regardless of what the rest of the board state looks like. Think "4th click and freshly broke from the last Keyhole run". With decent Archives ICE, that isn't an option and the corp just bought himself a turn to try to win/recover/whatever.