Kotlin does have Private and Protected. But by default it is Public (although one allow to type so). It allow one to omit the unnecessary thing.

Even though a language is better than the others, it does take time to transition. Today, many old languages are still being used, e.g. Cobol, Pascal etc.

Another point is, Java continue to improve as well. They starting to adopt more and more modern programming approach. Similarly C++ is also evolving.

If any of these languages stop evolving, very soon, it will be not be relevant anymore. But there will always be a minority of people will want to stick to them for life.