So far the only reason I’ve concluded is Java’s language designers’ egos were so damaged by C#, Swift, Kotlin, TypeScript, etc that after dogmatically denying the developer-productivity benefits of properties for the past 20 years that to concede now would mark the end of Java as a language entirely.
...I kid, but seriously I haven’t heard any compelling argument from the Java camp yet for refusing to add this feature. Object-properties are easily the lowest-hanging-fruit with the biggest productivity-gains.
Heck, even some of the most popular C++ compilers support object-properties as proprietary extensions.
I think the current future view is Withers ( https://github.com/openjdk/amber-docs/blob/master/eg-drafts/... ).
So I did some small standalone projects and demonstrated how much easier life was with this and other (more significant) changes. For example, we had loads of operational problems with dependency injection - the usual cognitive and debugging issues - so I threw all of that out too, along with the frameworks that implemented them. Things started booting in a few seconds instead of minutes and I’d say the lack of setters/getters was mostly done because I built trust in my team that I was making their lives better so they just followed me.
Probably not the answer you were looking for but there was friction from the devs and in the end I just showed them how much nicer life could be...
I think Java 11 and higher are reasonably terse/expressive without being overly dense.