You are one of four players in the group. You need to consider the rest of your group. If you and only you want to spacebar through conversations then demanding that the rest of the group do what you do is selfish. On the other hand, you are just as selfish if you and only you want to watch all the conversations.
I don't tell people that they can't spacebar through the conversations but I also don't skip through the conversations myself because I enjoy them as part of the experience. If a group wants to kick me and find someone else, that's their decision but I think it's a little childish considering that the cut scenes only add about five minutes to the length of the average flashpoint.
In my opinion, some players have become too impatient. They complain when I don't skip conversations. They complain when I pause to harvest crafting materials. They complain if I stop to pick up a lore object I haven't gotten before. It's always "go go go now now now".
Personally, I blame overdiagnosis of ADHD and its associated Adderall abuse.