There are good salesmen and bad salesmen, sorry persons. The good ones know the product and the bad ones try to ad lib their way through the whole process. I personally think that the person coming in to buy a car that day knows what they want and by the time he has got that far may know more than the salesman about a particular model, not always true but often this is the case. The bad salesperson is quite evident to the buyer and should be avoided at all costs, he will lose all interest in you as soon as you sign on the dotted line.
The initial sales pitch has often been done buy other salespersons at other dealerships and the buyer now knows what he wants and is now only considering the price at dealer A and dealers B, C etc. Salespersons are basically facilitators, they often think they just sold a car but the customer knew what he wanted and it all came down to price and availability.
Too many sales people are just drifters, and not professionals, they would have a hard time holding down a normal job.