Actually it’s not, and there’s a difference between talking to strangers for business, and talking to strangers in social situations.
On this, I'd agree. Plenty of salesfolks are quite introverted outside of work.
This is true. The average person on the subway or in a restaurant has no real malice or ill intent toward their fellow traveler/patron, whereas the average salesperson or business associate on the job is actively looking to hoodwink you.