It's okay if the reason is, "because we make websites and the programming we know is Javascript" or whatever. It doesn't have to be about some objective comparison, like optimization or whatever, which isn't going to be true or necessarily matter anyway.
However, mobile browsers will be supported with Unity 6 web exports, still experimental currently AFAIK, but that should become a viable option soon.
Hmm... Unity WebGL has worked correctly on Mobile Safari since 2013. Support has probably been flawless since around 2019. It has been supported in all the ways that matter for a long time.
From the article:
Android and iOS browser support has arrived With Unity 6 Preview. Now, you can run your Unity games anywhere on the web, without limiting your browser games to desktop platforms.
https://unity.com/blog/engine-platform/unity-6-preview-relea...