From a cognitive point of view, learning a large number of idioms is more manageable for <i>human beings</i> than having to reinvent the mental constructs from primitives every time. This human capacity of dealing with idioms is what called &quot;chunking&quot; in psychology (<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Chunking_%28psychology%29" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Chunking_%28psychology%29</a>)<p>Human has unlimited memory capacity and fast memory access, whereas human logical processing power is fairly limited and error prone. That&#x27;s why any real human language has a large vocabulary.