That's the POWER of MARKETING!
Put it this way, they set-up counters in shopping centres with beautiful set-up and packaging to entice the public. And the consumers like this kind of things - that's why it work.
It goes the same for bubble tea, its basically just some low-grade tea leaves mix with some low grade starch balls, colourings and sugar syrup packaged nicely to form a winning combination.
But as per all fads, it will die a natural death in due time.