To be happy.
I don't do meditation (and in fact get kind of irritated that practitioners of it seem to imply the only way to get in more control of your brain is through meditation), but I practice CBT. The idea is to be in greater control of your conscious and subconscious processes by being more aware of what's going on in your brain.
For example, I noticed that when people make suggestions on products I work on that have the potential to violate users' privacy, I tend to get defensive and argumentative over that point. Using CBT and practice, first I was able to identify the emotions that rush over me when that happened. Then, I was able to notice and acknowledge those emotions happening and finally I was able to control them and let them pass without influencing my behavior. The last step in the puzzle is finding out why that particular issue is so triggering to me.
After becoming aware of these things, I'm a lot less anxious, my relationships are much stronger, my communication is better, and I'm just in a better mood and happier in general.