Hello.
I just wanted to add my experience from D365 to this thread as its a frustration to our businesses, good old fashioned time and motion, reducing mouse clicks and time, this process increases the steps required, introduces risk of error, and information being missed from onward processes, ie include contact details with a type of Delivery on delivery notes, would not happen if the details were set as Business Purpose.
When you create an address you can set the Purpose/s in my case here Delivery.
Why would i then want to add a phone number to this 'Delivery' address with a Business purpose?
As you can see Address has a Delivery Purpose only.
The contact details section, from Add button defaults the purpose to Business and you can not change it

Having added the record, you then have to click Save
Then back to the contact info section and click advanced to change the purpose.
Lots of mouse miles and time spent.......
This is a multi step process for what should be a single step and as suggested below, the purpose should default from the purpose you have set for the address, in this Case Delivery.
When creating 10's of thousands of addresses a year and many more contact numbers this causes so much concern on time and room for error
please please fix this :-)