It isn’t deprecated because it was never standard in the first place.
HTML is (in theory) a semantic markup language. It describes the structure and semantics of a document along with relationships to other resources.
HTML is not supposed to describe presentation. A bunch of presentational features were added during the browser wars. Some of these became standardised. Most of them were subsequently deprecated when CSS came along.
CSS is a language for describing presentation. When you have a chunk of text that shouldn’t have a line break in it, that is usually a matter of presentation so CSS is the right place to do it.
The exceptions are usually handled by non-breaking spaces ( ).