Some of it may be inertia from early days of Android - for a long time I still had the Dolphin browser installed because for a time back in the Android 2.x days it was the best option around and IIRC included its own build of Chromium's rendering engine ("Dolphin Jetpack").
UC Browser is likely also available on devices not using Google Play where Chrome may not be an option.
UC Browser is likely also available on devices not using Google Play where Chrome may not be an option.