The answer to this question is quite hilarious yet true, in Astrophysicist chronicles battle over Pluto Dr. Tyson decided to exclude Pluto from the exhibits of planets because:
Because he considered Pluto to be an icy body rather than a planet.
An interesting and funny fact is that: Americans associate Pluto with the Disney character of the same name.
Most Americans Associate the Dwarf Planet with the Dog Pluto. But the main reason for Pluto to be considered a dwarf planet instead a planet is: Dr Tyson considered Pluto to be an icy body rather than a planet.