The names FIRST and REST are easier to associate with their behaviour than CAR and CDR, esp for somebody new to Lisp. The names CAR and CDR exist purely for historical reasons.

The Lisp FAQ defines CAR as: Originally meant "Contents of Address portion of Register", which is what CAR actually did on the IBM 704 and defines CDR as: Originally meant "Contents of Decrement portion of Register", which is what CDR actually did on the IBM 704. Pronounced "Cudder" /kUdd@r/ (as in "a cow chews its cdr"). The first syllable is pronounced like "could". It also tells us to Use (SETF (CAR ..) ..) and (SETF (CDR ..) ..) in preference to RPLACA and RPLACD. Likewise (SETF (GET ..) ..) instead of PUT.

I didn't discover Lisp until the mid-80s, when the Common Lisp dialect was available. This may be why I feel no obligation to use ancient (and obscure) names. Some other Lisps use names like HEAD and TAIL, which I feel are just as reasonable as FIRST and TAIL. Fortunately, Lisp usually gives us a choice. If we don't like a name for a particular function, we can do something about it. Unfortunately, it takes time to learn enough to realise this, and how easy it is. This is why I suggest that the names CAR and CDR are a problem - for beginners.

Obviously, my perspective will be very different to somebody who learned about Lisp years before I did. While I'd be far less experienced with Lisp than such a person, I can offer my experiences with Lisp, and the features I've had difficulty with. Obscure names may be very minor problems to you or I, but I suspect that we may be exceptions. I'm not entirely comfortable with names like CAR and CDR, but I know that such "trivial" things can bother some people enough to make learning a language difficult.

If we can make Lisp easier to learn by instead using names like FIRST and REST, why should we not make that effort? The only reason that I can think of is that we might not care how many other programmers use Lisp. I sometimes get the impression that some people who use computers enjoy using software that is obscure as possible. I'm not as patient with such software as I once was, and I'm not sure that if I discovered Lisp now instead of about 10 years ago whether or not I'd have bothered using it, when there are alternatives with would appear so much easier to learn.

Yet I'm still be more patient with languages like Lisp than most programmers that I know. They seem like a typical bunch, to me, but I hope I'm wrong. If I'm right, then Lisp doesn't have many friends these days, at least not for the platforms that I develop for. I'm not suggesting that using FIRST instead of CAR and REST instead of CDR will be enough to change that, but I'm sure that such things can help.