My guess is infrastructure, it's often very dated for running AI locally, and that's the only way to do it that makes any sense in terms of finance and security both.
Youre not wrong, there are some companies running on IBM AS400s but even if you address that, you still have modern companies with software systems that dont talk to each other at all. So even if you had an AI running locally, you cant give it access to all of your data because the people dont even have it unless they click around tabs. There's companies addressing this by unifying stuff like augment or mithrilis but it will take some time