Because it would not be backward compatible, eg:<p><pre><code>    el.style.color = &quot;red&quot; &#x2F;&#x2F; write
    console.log(el.style.color) &#x2F;&#x2F; read
    el.style.color = &quot;green&quot; &#x2F;&#x2F; write
    console.log(el.style.color) &#x2F;&#x2F; read
</code></pre>
Outputs: &quot;red&quot; then &quot;green&quot;.<p>Batched: it outputs &quot;green&quot; then &quot;green&quot;.