This is definitely a difference between people that believe the work they do is important and people just punching a clock.
I teach at a community college (salaried) and my partner works as staff in the same school (hourly). She works her ass off, but when she gets to the end of the day, she is done and leaves work at the office, so attending meetings is no big deal to her. Meanwhile, I've gotten involved enough in peripheral committee work that I regularly stay up working until 1AM because there are literally not enough hours in the day to get done what needs to get done. I could try to leave work at work, but I'd be hanging students and fellow instructors out to dry, so that's not always an option.
If HR can't understand that, then it isn't a decent work environment to begin with.
You can always try to explain it by calculating the cost of you sitting uselessly in meetings. Your hourly wage X amount of hours in meetings. I'm sure they will take your side.