E2E tests are usually skipped for one of two reasons. The first reason is that they are difficult to write. You have a lot of extra setup to get these tests to run, including a completely different test runner than what you normally use for unit testing. If not a different runner, they at least need to be a separate test run and not included in your normal unit tests.

The second issue is that E2E tests are fragile. Any change to the system and these tests break. They are not commonly run all the time like a unit test is and so the broken code will not be noticed until they are run in the production environment.

For these reasons we generally do not write that many E2E tests, if any at all.