Yeah, in your opinion there's no reason to disallow Chummer/HeroLab and dice-roller apps, Guns. That doesn't mean your opinion is correct, or that other perspectives don't have merit.
One good point is that using character generator/builder apps gives people the option to not actually read the books and see how things are supposed to work. I'm getting tired of it myself, since a ton of people in a chat game I'm in have been handed Chummer and told to go wild when they have no experience with the system or setting whatsoever. You can guess how it goes.
I've seen errors in these programs cause a ruckus too, which is annoying. When someone with little experience with Shadowrun running a game says 'the program says you can't do it' instead of actually looking in the book, that's a problem.
Hand-jamming your characters actually makes you go through the book, which also means you pick up on other things along the way.
Another good point is that I've totally seen people mess with those apps and cheat (changing settings to give them more favorable things, putting in wrong numbers, actually messing with the code, etc.). I'm getting tired of that shit too.
Dice roller apps have the same kind of problem; I've caught players fudging the shit out of their little apps or rerolling things on the sly until they get their favored roll, which is harder to do when they roll a handful of dice in front of everyone and we can count the 1s before they can do some hand-shielding bull-shit.
All in all, there's plenty of valid reasons to ban any and all character creation or dice-rolling applications or programs at your table. I'm not saying it is right or wrong, though I personally do it.
As far as players glued to their screens go (there is a difference between the occasional tech-check and being glued to the screen), you can totally tell them to put their shit down and listen. If they don't, they reap the consequences of their actions. If you don't want to kick them out, don't. But don't tell them what they missed either. Obviously their character was licking windows, playing Shadowrun's version of a mobile game, on the phone with someone else or something while everyone else was doing what they should have, and they missed their opportunity. Throw surprise on them in Initiative, have them give offense to people who expect attention to be paid to them, etc. Rub their nose in what they're doing wrong until they either get it right or get out. It's the only way to do it if they won't be talked out of it and you don't want to just kick them out.