1. Less time, more UI development 2. ZK is much flexible in terms of creating the wrapper on top of it (Using the java code only) than any other JS framework. 4. Primefaces(JSF) is somewhat reaching to all the needs zk fills, but application built on primefaces cannot handle heavy load of user, and lags in response. 5. We had efficient java developers to work on a UI framework based on Java faster (as time was very less). So, Hiring a UI developers and experimenting on JS/UI technologies was not so useful.