Why can't put newly added contact into group while on my iphone

Working on my macbook, I have already set up several  contact groups within the program Contacts. My iphone and computer sync everything correctly when I connect them. On my macbook, I can add contacts and shift contacts as I see fit into different groups. But say I'm out and I add a new contact to my iphone. There is no way to add this contact to a group. I have to wait until I get back to my laptop and connect them so they can sync, transfering the new contact data to my computer. Then, in Contacts, I can place that new contact into the correct group(s). Then I have to re-sync the iphone and computer to transfer that new grouping back to my iphone. It's a crazy hassle for what seems could be a simple software fix.