Upgrade to 15.04: What happened to my gnome-terminal tabs?

If you want to know how to fix this problem, the new version has the option to open all new terminals in a tab. Go to Edit -> Preferences and then change "Open new terminals in: Window" to "Tab".

Just downgrade to good old 3.6.2 like me did.

If you have a 64-bit install:

wget http://archive.ubuntu.com/ubuntu/pool/main/g/gnome-terminal/gnome-terminal-data_3.6.2-0ubuntu1_all.deb http://archive.ubuntu.com/ubuntu/pool/main/g/gnome-terminal/gnome-terminal_3.6.2-0ubuntu1_amd64.deb
sudo dpkg -i gnome-terminal_3.6.2-0ubuntu1_amd64.deb gnome-terminal-data_3.6.2-0ubuntu1_all.deb
sudo apt-mark hold gnome-terminal
sudo apt-mark hold gnome-terminal-data

For 32-bit:

wget http://archive.ubuntu.com/ubuntu/pool/main/g/gnome-terminal/gnome-terminal-data_3.6.2-0ubuntu1_all.deb http://archive.ubuntu.com/ubuntu/pool/main/g/gnome-terminal/gnome-terminal_3.6.2-0ubuntu1_i386.deb
sudo dpkg -i gnome-terminal_3.6.2-0ubuntu1_i386.deb gnome-terminal-data_3.6.2-0ubuntu1_all.deb
sudo apt-mark hold gnome-terminal
sudo apt-mark hold gnome-terminal-data

Downgrading kinda works but it isn't the best option since newer versions always have bug/security fixes.

The best option for you is installing mate-terminal, which is a regularly-updated fork of gnome-terminal that still has tabs and all of the bells and whistles you're accustomed to. I've got it running on my system now since gnome-terminal removed that tabs feature.

It's nearly identical but it's not missing features! Hooray!