probably because there reliable, easy to do a top end on w/o remove the motor. they start good, no one is afraid to jump on one and go,
their simplistic in basic design.
everything new is much more for much less.
i like my 50v moby but not everyone can turn a wrench, so puch for a first bike makes the most sense, for a first bike.
when someone asks '' what should i get '' puch will come into play. pronounced like BOOK