They don't use a chip/pin system for credit cards yet either, of course.
There isn't really anything inherently safer about having not using a PIN for a CC (it only really protects against using a physically stolen card before it's been reported), and I'm sure it would slow things down a bit (significantly, I dunno).
RE, Tap - that won't work if the charge is over $100. So if you have 2 passengers, its going to be too much, and you'd have to use a PIN.