Reason is a combination of Google making Play publishing something between hard and impossible and no active maintenance. The app saw no significant development for a long time and without Play releases I do no longer see enough benefit and/or have enough motivation to keep up the ongoing maintenance an app requires even without doing much, if any, changes.
Sad to see it go. There is a fork but seems not so great considering they are looking for active maintainer. Still better than nothing. Need to check it out as it has some enhancements.
Planning to close my Google Play Developer Account. Please say hi if you are interested in obtaining the latest gplay release files from me to help in publishing this app