Yes I think the only way to delete the pre-installed apps on your device, is to root the phone itself. I don’t think any phone manufacturer would give you the option to delete the pre-installed apps.
That’s right. They’re using those apps to set their phone apart from all the different Android phones that exist. Many phones with pre-installed apps would mostly have something where you’d be urged to submit your information for login. I think that’s part of how they’re advertising for their other products.
If you can’t delete it with the Application Manager then they were put on by the carrier, you’ll have to root your phone which is very easy (Just make sure you know what you’re doing) and then install an app which will allow you to delete them.