How can banks be sure that computer, the browser, the os people use is very good at security? It should scream the people that phone is rooted. But, denying se

How can banks be sure that computer, the browser, the os people use is very good at security? It should scream the people that phone is rooted. But, denying services is inimical. Its not just banking app I have started to see a lot of app behaving differently when phone is rooted. Rooting generally means people can mitm app, which app developer obviously doesn't like. Its more about control than security in my opinion.