On the other hand, a relevant person being out of the meeting and out of the loop can easily mean that the other 7 people spend the following week on something that shouldn't have been done in the first place.
It's easy to spend a hundred productive engineer-hours that eventually add up to a negative added value.
True indeed, and arguably that's how I spent Wednesday and Thursday this week, but you're a little close to saying "although meetings tend to waste time, that's excusable because other things aren't perfect either".
I'm saying that deficiencies in information exchange are even more likely to waste (a lot!) of time than meetings.
It's desirable to reduce time wastage at meetings, but it's not ok to do so by simply randomly not appearing to them - if you want many people to skip these meetings, then you have to have a solid alternative on how you'll get the info exchange.
It's easy to spend a hundred productive engineer-hours that eventually add up to a negative added value.