According to Kernighan in UNIX: A History and a Memoir, the Unix team was constrained with regards to hardware capital at the time of Unix's creation. The Multics team got to use a fancy GE-645 (36-bits!) while the Unix team had to beg for "cheaper" systems like the PDP-7 and eventually an 11. Thompson has a great quote about how ultimately he was thankful they didn't have as much money to play with as the Multics team did but at the time he was annoyed he had to beg for a PDP-11. Fun book!