Website vs Mobile App, what is best for me?

I am working as a web analyst at ……., working on their website. As I also advised the team that you should also create a mobile app as it facilitates more users. But they refuse the idea that it wouldn’t work because it is already working best on the website. Kindly give me advice on what I am saying is right or wrong. If I am saying right then tell me tricks that how can I convince them