I would limit that complaint to your specific scooter, since I'm on my 2nd Kymco, and while
one DID come with low quality tires (Agility 125, CST tires), they did not crack or wear
unevenly or show any other faults when I replaced them in 2010.
At that time, the scooter was 4 years old, has sat on on a showroom floor for 2 years
and I've put 7000km on it from 2008 to 2010 before replacing them, purely because I
wanted more grip since I ride all year round.
On the other hand, the Kenda tires that I got with my Downtown 300 are great.
I've also ridden a test bike with 6000km on the same Kenda tires and was amazed
with the grip. I did NOT expect that. I got worse tires on my 650cc Kawasaki!
p.s. Cracked sidewalls usually happen because of under-inflation.