I don't see a strong reason for a software developer to need a phone:

- Async communication (slack/email) can be checked at your computer.

- Voice calls are usually done with your computer anyway.

- If you are on call, an old-fashioned pager can be used.

Frankly, although I do have a smartphone, I wouldn't want a job where I was required to use it, or one where I was expected to be available at all times unless on call.