Web components come with additional complexity, heavy use of custom element definitions are more complicated to manage.

It’s more than just an aesthetic preference

But if you’re not really using web components it’s harmless but it’s a bit odd and pointless.

HTML had custom elements before Web Components (the complex modern JavaScript & Shadow DOM thing) came into being. https://www.w3.org/TR/2016/WD-custom-elements-20160523/