The [marquee element](https://html.spec.whatwg.org/multipage/rendering.html#the-marquee-element-2) is still in the spec and unlikely to be ever un-shipped. One reason is specifically legacy websites. A lot of websites of India are still using it and for webcompat reasons, we can't just break these sites.
You can see two parts of it:
* As an author, do not use it, the intent is to remove it.
* As a browser implementer, it will not be possible to remove it for a very very long time. Because legacy websites don't go away that easily and in the case of marquee, a lot of university/gov websites are [using it](https://www.chromestatus.com/metrics/feature/popularity#HTMLMarqueeElement).
If you still want to give another example, [`<blink>`](https://caniuse.com/?search=blink) has been removed and is no longer supported by any modern browser.
To make things a bit more interesting and add a fun bit of trivia, JavaScript there's a memorial for this element: every string in JavaScript has the `.blink()` method, which returns the given string wrapped in a `<blink>` element.
Also, a [nighttime story about blink](http://www.montulli.org/theoriginofthe%3Cblink%3Etag)