I'm not seeing any practical benefits mentioned so this sounds like dogmatism to me. Using an img tag can sometimes just be more practical (e.g. if you're using a CMS or for use with a JS plugin). Google Image search definitely cares about images as well. I agree separating style from content has benefits but doing this at all costs isn't worth the time in my opinion and a few img tags seem harmless to me. It reminds me of how people are against JSX on principle that code and HTML should never be mixed without attempting to consider any of the benefits.