https://www.w3.org/TR/WAI-WEBCONTENT/#tech-expand-abbr
W3C #a11y specifies that abbreviations have an expansion of the abbreviation where they first occur, and that *requires* the abbr tag.
In addition to screen readers, there are issues of cognitive disabilities. Some people have trouble remembering what abbreviations stand for, even common abbreviations. It doesn't help that social media is full of people giving incorrect expansions of abbreviations.
The abbr is a very important tag. Visually it may not make a difference, but semantically it is of tremendous help to assistive technology.