They also clearly worked in this edition to remove the so called "decker pizza" problem. That's why they established the strategy of having the decker with the team, moving in and direct-connecting to everything in AR. It is established that causing that kind of situation where one player does everything while everyone else waits around is a bad thing. They are clearly trying to avoid those kind of schisms. Again I agree with Rhat though; when a decker ends up still away from the team in a host or the mage is astral projecting, the players are not forced to wait. Often it is the best idea (such as if you're having the mage check it there's guards around a site before approaching) but if they have other things they can do, there's nothing stopping them. Usually astral scouting is done without rolling initiative in my experience, since it doesn't need to be so precise. With a decker in a host, however, with IC rolling to spot them every chance, you do need to roll initiative. At this point though, everyone should still be doing something. Every time the decker loops a camera feed, the team is moving past it and keeping a look out for physical obstacles in their plan. Again, no one is prevented from doing anything because of the nature of a decker.
In combat though, unless your player is an ass, you can't just keep moving on. Everyone rolls initiative and you've got to deal with the threats right then. Combat sort of "overrides" all other objectives, since that's kind of the idea-- The security or whomever is shooting at you with the intention of forcing you to stop what you're doing and either shoot back or retreat. Everyone isn't able to keep doing whatever, it involves everyone in the group all at once (who's physically present), and so it's reasonable for everyone to get a chance to contribute... Meanwhile, that combat monster with 30+ initiative is still going to make everyone shit out their teeth by the end of it. That player is getting to shine, still dominating, and the other players are also able to contribute. No where near the level of the street sam or phys. adept, of course, but enough to help and enough to feel like they have a reason to be there.
Combat is seriously a lot different from hacking and astral projecting; and I'm certainly not defending those two when they do end up separating play too much. It's a bad thing to do, no one wants it to happen, and the game's rules have been trying to fix the most common version of it for 5th edition. It just really, really seems unreasonable to just institute another rule to bring that factor back in another section of the game.
Ugh, I'm getting too worked up about what is, at base, an optional rule. Sorry. Use it if you want, I just want to warn people that it could really take the fun out of the game for other players in your average campaign style.