And a prime only user might wonder what a photographer that isn't a prime only might be able to do if he was prime only.
The point is, a fully equipped shooter CAN shoot with primes only, as an exercise, whenever they want. They are just not limited that way.
Maybe it takes shooting only primes for a while to hone your technique, or help you see things a little differently. That's fine. I agree to that. I've been there. But once you have achieved your objective and grown from it, why not continue to challenge yourself? Why keep yourself stuck in that primes-only exercise? In the same way, adding a zoom back into your lineup after years without one can help you "see" things differently again. Use it in ways you coudln't have without your primes-only experiences. And you grow. Again.