Working on your laptop while you're in a meeting is one of the most rude behaviors possible.
If you have something more important than the meeting, decline the invite. If you're too busy, decline the invite. If you're not going to be utilized for enough of the meeting for it to be useful to you, decline the invite.
Don't be that asshole in the back responding to emails or working on some unrelated project and not listening to what's going on.
The assclown in the meeting on his laptop is generally operating at between 0 and 50% efficiency; about 25% on Google Chat and 25% in the meeting asking questions that have already been answered. Let's be generous and say 50%, but its probably less.
Now, that's 1.5 hours lost in the meeting plus preparation, but the meeting needs twice as much time to get the same done so that's 2.5 hours now times 8 people per meeting.
It's probably exponential though, since laptop people have to talk to other laptop people in the meeting at only 0.5 efficiency. So its probably more like 0.5 to the power of the number of people on their laptops.
Yes, the problem is one of poor management where the system starts working against itself.
The developers don't have laptops, so we just lose development time when we're in meetings. Although we generally get just enough work assigned to us that we can still work only 40 hours a week, so I'm not really complaining.
The programmer equivalent attitude is "this code is horrible, it's due for a total re-write." Re-factors and re-orgs are the same things, but there's few regression tests for business besides "oh crap, we lost a bunch of money all of a sudden" which is a lot closer to coding directly in production.
For example, I was stuck in a two hour support call meeting the other day, and I really only had to be passively listening to it and speak maybe four or five times briefly. I was designing puzzles in my notebook the rest of the time. They don't give devs laptops, so I couldn't get real work done.
But hey, I've been in plenty of classes back in the day when I didn't have to pay close attention and only had pen and paper to keep me entertained (I drew, wrote stories and poems, designed games and databases, etc), so it doesn't bother me too much.
There's a reason why there's a full team of BA's and they can't write up work fast enough to keep the devs busy, and I think this is part of the reason. But there isn't enough of a push to change things, and it seems like most people would rather communicate in person here instead of via email when possible.
Many varieties of rudeness are culture-specific.
No matter how popular it is to say that all meetings should only include people who will need to be 100% engaged the whole time, should only ever be attended entirely at each participant's discretion, etc, things do not always work out this way.
If I'm attending a big status meeting where I go second and only need to listen to the first and sixth updates or when my name is mentioned, guess what happens for the rest of the time?
But please, continue thinking that people are naive for not being rude.
Or maybe don't waste people's times with useless meetings or with an unfocused meeting
Or maybe don't make the meeting take longer when discussing things that could be decided quickly by fewer people or I dunno, just wasteful meeting behaviours like repeating the same thing several times...