Your question boils down to the more general question: why would I use a different programming language?
Obviously, the answer is that it provides benefits to you -- and Kotlin has many benefits compared to Java in terms of language features, code readability, and code quality. I encourage you to take a look at Kotlin if you're interested.
That being said, if you're happy with Java, feel free to stick to it. In the end, you just need a programming language you can work with effectively. IMHO, you can work more effectively with Kotlin though once you're really familiar with it.
Terry Broman wrote:Convince me I need to learn yet another programming language.
The book "The Pragmatic Programmer" encourages developers to grow their skills by setting a goal (p14) to "Learn at least one new language every year. Different languages solve the same problems in different ways. By learning several different approaches, you can help broaden your thinking and avoid getting stuck in a rut. Additionally, learning many languages is far easier now, thanks to the wealth of freely available software on the Internet (see page 267)."
It's a lofty goal. I've tried to pick up new languages as often as I can but it's more like every two years or so. In addition to using Java, Groovy, Scala, and Clojure at work, over the years, I've also learned Go, Rust, Elm, and Kotlin, and a bit of Ruby and SML -- via online courses and tutorials. I highly recommend reading that book and trying to follow its advice (it covers a total of eight goals across pages 14 & 15).
I spent the morning putting in a comma and the afternoon removing it.
-- Gustave Flaubert, French realist novelist (1821-1880)