Because the xUnit consultant crowd worked a lot, it is easier to make unit tests (which fossilize your code) so there's a lot of tooling around it. And the reliance on external services with no sandbox or ready to use mocks mean E2E is harder to implement. But being harder just mean you have to do your job.
When I buy your software I don't care about how you implemented some pattern. What I care is that when I click on this gizmo in that situation it does what it should in some time-frame using some resources.
Yes.
> and why it exists?
Because the xUnit consultant crowd worked a lot, it is easier to make unit tests (which fossilize your code) so there's a lot of tooling around it. And the reliance on external services with no sandbox or ready to use mocks mean E2E is harder to implement. But being harder just mean you have to do your job.
When I buy your software I don't care about how you implemented some pattern. What I care is that when I click on this gizmo in that situation it does what it should in some time-frame using some resources.