If I was to hire Sanders & Smith. I would have next to no research power 5% if I'm lucky & next seasons car would be a golf kart or a shopping trolley.
So what is the point of having them on offer for hiring?
Is a low rating car, faster than a high rating car?
Those two actually could have a use if you'd be quite in debt and want to do some season(s) of cash flow without regard of performance but still have too long contracts to wait for auto-replacement. For all staff in between those and the mentioned useable 4.5+ star ones I can't see even such a tiny potential use, though.
Level 19's with 4.5 star have equal strength in research as 5 star staff, but Level 18's with 4.5 star show up with 4.5 research.
If I was in debt and needed to make changes, I would much rather have a good car and bad drivers to save money, rather than paying good drivers big money and having a bad car.