A:Answer 1. Use one device for personal and work number
2. International travel made easy. Let's say use eSim for a home network and nano sim to use the local sim of the place you travel to. Usually much cheaper than roaming charges.
3. Some areas have bad coverage, if you move a lot, work or pleasure, having 2 different providers will improve that.
4. Just have 2 lines for whatever purpose you may require.