I think that comparison is a bit off. Internet Explorer cannot be removed without damaging Windows or affecting other programs which depend on Internet Explore

I think that comparison is a bit off. Internet Explorer cannot be removed without damaging Windows or affecting other programs which depend on Internet Explorer's files. You also said yourself it is "pre-installed". You are not required to be a Google+ user in order to use Gmail, and you obviously won't see integrations in Gmail unless you have a Google+ account.