There are technologies that solve one problem better than others or for example you already have modules written in Java with all business logic, integrations,

There are technologies that solve one problem better than others or for example you already have modules written in Java with all business logic, integrations, security compliance (and what not) and it would take forever to adopt them in another language. Same for Python and ML. Many companies work with different tech stack and for them is also a benefit to have flexibility in that manner.