We use Apache Maven because it is a standard. Gradle is very good alternative, but Gradle doesn't provide any advantage for our project. Gradle is slower (without running daemon), need more resources and a learning curve is quite big. Our project can not use a great flexibility of Gradle. On the other hand, Maven is well-know tool integrated in many IDEs, Dockers and so on.
I also prefer Maven as building tools. Using Apache Maven is getting better compatiblity with the old versions. I almost need not change any configuration since Maven 2.0 and run the project under the newest Apache Maven 3.6. But it is impossible in Gradle. And somebody could say Gradle Wrapper fixes this problem, yeah, for these years that I had used Gradle sometime, the size of my download Gradle distribution and cache under my home directory is over 20G, it is terrible, it wastes a lot of my disk.