Because it’s cheap, long lasting, tastes good and it’s a lot of fun.
But fun is the big one.
Go back and read about what the inventor of bubblegum, Walter Deimer, did when he introduced bubblegum. He made it one flavor and one color and then pretty much promptly forgot about those details. What he did was teach his salesmen how to blow big bubbles then had bubblegum contests for kids at his house.
He knew he had something way different than just some other new kind of candy. He had something that was now a challenge to anyone who saw someone chewing it. A challenge that said “try me and see how big a bubble you can blow.” Which of course immediately led to the next guy saying “I can blow a bigger bubble than you.”
Walter Deimer may have invented bubblegum, but more importantly, he invented the never ending challenge that has powered his product to being one of the world’s most interesting success stories.