This is a library thing, not a language thing. And it&#x27;s a performance tradeoff: they could have shipped with a concurrent map only, that is 1&#x2F;10 as fast as the current one, but never causes a data race. However everyone that <i>isn&#x27;t</i> doing anything concurrently would be paying for it. Not very clever. I trust the class library designers thought this through. They reached the same conclusion as pretty much <i>every other library designer in every other language</i>. For the same reasons.