The reason they make it hard to remove is (1) otherwise malware could easily disable it and (2) must people should not be trusted with such decision anyway.
Norton sucks and is pretty much objectively malware, but there's one key difference: because win defender is bundled with my OS (and the security updates I have to install, it can change itself, re-enable itself, etc. Malware can still disable it with admin, they just make it hard for a user with admin. The operating system can only do so much to save a user from himself. Maybe some sort of developer mode, a la android?
The reason they make it hard to remove is (1) otherwise malware could easily disable it and (2) must people should not be trusted with such decision anyway.
Also, have you ever tried to remove Norton AV??