Because you can usually rack pull more than you deadlift(unless
your grip is weak), it’s able to overload the posterior chain, grip
and upper back. It’s also a great option for people with
flexibility issues that prevent them from doing full deads. The
setup for rack pulls is slightly different from that of a mid-pull
for deadlift, so the carryover from a rack pull to a deadlift
lockout isn’t as much as popularly believed.