A surprisingly large number of landing accidents are loss of control
after the airplane slows to about 30knots or so (often lower), which
makes a lot of sense when you think about it.

Your land based airplane has two basic modes of operation: tricycle
(forwards or backwards) and airplane. When you're flying, it's 100%
airplane, and when you're stopped, it's 100% tricycle. In between, you
get varying ratios between the two.

Because of this, as the airplane slows down (well below stall speed)
you'll get into areas where aircraft control is a little different.
Doing a full stop landing allows you to practice in this arena, but
during most T&G's, the airplane never get's that slow.

The other side is the safety related to reconfiguring the airplane on
the roll. If you're taking your eyes and concentration away from what
you're doing (flying/rolling out) bad things can happen quickly.

Just my two cents.

-Rob
www.scarylittleairplanes.org