You need to set mode http
. This should work:
defaults
mode http
frontend main
bind *:80
use_backend drewgrosscom if { hdr(host) -i drewgross.com }
use_backend drewgrosscom if { hdr(host) -i www.drewgross.com }
backend drewgrosscom
server app1 127.0.0.1:8000 check inter 5000 rise 1 fall 1