A marriage of Unix with statistical computing was not initially looked on very warmly by either side. Unix began on a 16-bit machine with relatively primitive facilities for numerical computation. The originators of the system felt (probably correctly) that statisticians and numerical analysts didn't have enough rapport with their approach to be appropriate guests on a crowded machine.
Aside from technical issues, there was a definitely different mindset at the time between the two groups.
All this started to change when experiments began on making Unix portable, and in particular on porting it to 32-bit machines. It was almost immediately clear to the S folks that here was the sort of environment we needed to pursue portability for S.