We have John Mayall and John Mayall and the Bluesbreakers. Shouldn’t these be merged?
John Mayall and the Bluesbreakers would be John Mayall - credited as John Mayall and the Bluesbreakers.
Now everything is separate and I find it very confusing
No, as one is a person and the other a group. If they were merged it wouldn’t be possible anymore to indicate that he is/was a member and who the other members are/were.
This seems yet another situation where a consolidated view for eponymous groups would be very handy: