All competition is about who is the best. Competitors of any real sport don't play just to improve their games and give exhibitions. They want to prove they are the best. And the only way to prove you are the best is to have a "title fight".
If I say I am better than you, then I should have to play you to prove it. Not having a championship for chess would make chess a joke.
There are sure to be some, maybe many? who play with the hope of one day being "The Best", and they are wished all the best if thats there goal, but there are also many who play just for the adrenalin in the challange, the enjoyment of mutual learning, or to pass the time observing the many variations in play, or maybe one of the many other reasons, other than being "THE BEST".
The claim that chess would be a joke without having a championship, is subjective observation.
Not everyone likes the taste of Lobster, but hey that just leaves more for me.
I remember all the world championships since the second Botvinnik-Smyslov match and have played through most of the games going back to Lasker-Capa. However, I haven’t bothered with any since the Fischer-Spassky match because they ceased being of interest me. I don’t know why; they just aren't. I have the same nasty attitude towards most GM events these days. Perhaps it’s because of the avarice of the players and organizers?!