Always existed implies at least on the dimension of time infinity and as finite humans we cannot really comprehend that. Therefore I think there is a bias for us to favour an actual beginning and eventual end to the universe. God can also be considered infinite so again our ability to comprehend that aspect is beyond us.
The fact that we can’t conceive or understand infinity is evidence of a Supreme Being. Just the fact that He always was and always will be is too difficult for us to imagine.