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.
Maybe it was because Alibaba operate a huge payments service network? This would be like PayPal making their own browser and having a load of vulnerabilities in it
I only posted it because it didn't mention Alibaba was the parent company in the article.
Maybe the article author would have had more luck getting a statement from Alibaba since it has a more significant international presence compared to UCWeb Inc.