SIMPLY PUT: WHAT! Do you really need a reason?!
ok...
To keep your mind actively seeking new discoveries...
and, to make the day whisk along...
and for those of a more practical mind-set: to show the best version of you...
and it usually helps others to be cheerful too

like anti-voodoo karma
and for those of a much more practical mind-set... because you just met someone fun while being cheerful

(or at least i did so you can to)
and
because all the fun and amazing animals, nature, art, technology, goodies, snuggles, food, opportunities, people, stories, music, and activities twirling about the universe...
or
because it beats being uncheerful by about 1000:1
etc. etc.
----
or because maybe there is just one person out there who you wonder about (like a Chelsaroo in my case who i met 10 years ago and still wonder about a few times a year probably because i kept bumping into her a few times a year for 10 years with consistently irksome/unfortunate/empathetic/odd feelings) and who still hasnt seen the real you and needs yet another simple reminder of just good old fashion cheery choo choo behavior to open up her soul and maybe help her apply a little more of that happy helpful cheerful charm to an important part of her life ...

just being cheerful about all those strange things in this screwy world (snicker)
(For musical references, John Lennon sung "Strange Days" and the Beatles also did "Day In The Life", and The Doors sung "People Are Strange", and Pink Floyd threw "Shine On You Crazy Diamond" into the mix) and Bobby McFerrin later sung his basic "Don't Worry Be Happy" tune... and Moxy Fruvous has a few great zingers, like "Once I Was The King of Spain" and and they covered Dr. Suess' "Green Eggs and Ham", but perhaps if I am lucky enough I'll be able to describe the fun girl I recently met with Moxy Fruvous' "My Baby Loves a Bunch of Authors"
"Zounds! Zorched by Zarches, Spaceman Spiff's crippled craft crashes on planet Plootarg!"
For Sale: Ninja 600 with parts bike, needs minor work, $30, no title... (GEE THAT DOESNT RING ANY WARNING BELLS DOES IT?)