Default [Q] why can't Stock Contacts app be replaced by 3rd party app?

with reference to Stock Touchwiz 4.4.2 rom on Note 3 - I'm trying to find a better interface for adding new contacts and have tried Contacts+ and exDialer. However, what i realize is that whenever I hit 'add new contact' in either app, it directs me to the default samsung add contact UI.

after i tried freezing the stock Contacts app using TB, both apps tell me 'there is no available app for this action' for adding new contacts.

any idea why and is there any alternative to this issue?

Thank you.