I wonder why the option wasn't built-in, because it is a known thing for chrome extensions, people often do not want intrusive behaviour by the extensions so the majority of extensions using numbers on the icons have to ability to hide them.
Millions of years of evolution, we were hunters, so everything that moves like that is distracting. That is basic UX, notifications and moving things are the most powerful and the most annoying thing, that is why people have the ability to customize them. A moving thing like numbers with that bright orange there clearly makes you watch with your peripheral vision and breaks your focus and flow.
All extensions like AdBlock Plus, AdGuard and many more that like numbers on them, have the ability to disable them as they know that.›