This is also something I also question from time to time.
I think having everything in one place would help with efficiency and limit complexity. However, I have multiple accounts for investing and banking and justify keeping them separate for the reasons of having options (switching, moving my business elsewhere) and not being at the mercy of one corporation, spreading out my risk of outages, hacks etc.
The big banks have physical presence in my area that if needed I could walk into and talk to someone face to face. However, lately the staff at branches are not as knowledgeable and having less influence at solving issues or problems.
I will likely keep things separate for now because I enjoy crunching the numbers and doing the work, however I would not rule out consolidating in the future.