Why do people go to meetings when they don’t want to or need to?

I was at a meeting today and I didn’t really fell a part or i had much to contribute to the meeting. so i listened followed the conversation and asked questions when I didn’t understand or something was unclear. I had read the minutes of the previous meeting and the agenda for the one coming up. My one bad habit in meetings is regularly checking my phone/twitter. but when I say often maybe once in a 2hour meeting. (yes thats once too often but still.)

I don’t really see this stuff as rocket science.

Yet I have meetings with people who in a group setting cannot have a meeting. it ranges form playing on phones, not contributing when asked, not preparing anything, watching off topic youtube videos during meetings, to actively having conversations on the other side of the table.

If you don’t want to be at a meeting don’t go

But in meetings sometimes i can be like that Often in meetings I will take notes on my phone. it is handy as it allows for syncing later or I can e-mail my notes to myself. I wonder if people assume I an just playing games/surfing internet/etc on my phone? sometimes i will be

Should I get annoyed at someone doing what i sometimes choose to do?
what if at every other meeting i am the annoying one.