Having gone from living with my parents for over 20 years to living with my fiance-turned wife for several years after that to now living alone for the last 3 years I can honestly say that living alone, at least for me, is by far the best. Here are some reasons why:
1) You can be as loud as you want
Want to play Mass Effect 3 in glorious 7.1 digital surround sound all night with zero guilt or need to consider someone else? Have at it!
2) Do your chores when you want to (or never).
You can do them at your own convenience and pace, without ever being nagged or criticized.
3) Smokers can smoke in the house all they want if you don't care.
I have friends who smoke and they were never allowed to smoke in the house before. Now? They can smoke in my basement all they want- this is especially great for them in the winter.
4) Sleep wherever, whenever and always uninterrupted.
No one will hit you with "when are you getting up" or "why don't you come to bed, it's late?" If it's your day off and you want to sleep for 15 hours....you can!
5) No one but you eats your food.
No more "who ate my taco? I was saving that!"
6) The temperature is set to EXACTLY your preference at all times.
And NO ONE complains :) My house is 64 degrees this winter. Saving tons of money on heating and no one is telling me to turn it up because they are cold (meaning of course that I have to be too hot....no thanks).
7) If you play an instrument you can play whenever you want.
I play the drums and nothing is more glorious than being able to just PLAY when I feel like it.
8) If you missed the lesson on sharing in kindergarten living alone is for you.
That family size box of overly sugary, diabetes inducing cereal? All mine, mine, mine!
9) Come and go as you please.
Go out whenever you want and have no one to answer to (or ask).
10) Have people over anytime you want.
There's never a time where you have to "check" with someone else. I can have an impromptu jam session with a guitarist friend, something that would have been nearly impossible before.
Living alone isn't for everyone, but for people like me, it's GREAT. Everyone should at least try it once in their lives.