I have a few developers that can't wrap their head around too much languages without popping one out. The less variability we have, the more robust the final code will be. Theoretically, all developers are ideal learning machines with a robust CS background and a powerful abstracting mind with infinite time to learn and jump around languages at will, with perfect understanding of each language caveats and idiosyncrasies. In practice, one has to build stuff. This kind of things, while not a perfect solution, allows my team to produce better code more reliably.