The ability to sync all contacts to phone
Having all the contacts in your phone is great for making calls quicky and efficienty when on the run. It's also great to have them on your phone for times when you need to share a contact with someone. Most devices can handle upwards of 50,000 contacts without any drama. Picking which contacts to sync based on their tags is important as well. This gives the ability to preclude contacts that are not needed as well.