The pinion gear turns the rack. In most vehicles this part is grease lubricated, not lubricated with power steering fluid. The power cylinder, however, holds powersteering fluid. If the lack of fluid were to cause binding, that might be the straw that breaks the camel’s back. I mean, you’re already over exerting yourself as it is and the extra effort required if binding occurs (especially if you’re in the middle of a turn)–could be catastrophic. That’s just [i]binding[i/]. What if it seizes?