Why only on the JVM and not iOS (Apple) nor Microsoft nor Android?
Apple's and Microsoft's mobile operating systems are closed source while Android's (Linux based) is open source yet is becoming more closed source with each release from Google. Closed source operating systems can easily contain backdoors allowing listening in on encrypted communication by getting copies of the messages before encryption and after decryption performed in applications. Beginning in early 2019, Puri.sm will provide mobiles that can run JVM applications just like laptops with no proprietary code. Until then, we recommend Puri.sm laptops and other Linux laptops.