Why cant we use [DS_FROM_EMAIL] In the "List" From email Settings

[mercuryyy]

So when you set the list "From email" and "From Name"
Those values get sent to the headers, so if you send from multiple delivery servers and each delivery server has a diffrent name and from address those get inserted into the headers and lower deliver.

Why cant we just set the list, default sender name and sender email to [DS_FROM_EMAIL] and [DS_FROM_NAME]

 

[twisted1919]

That's because most of the servers will then reject your emails.
There's a setting in your delivery server, called FORCE FROM which by default is set to Always. You can set it to Never to do what you asked above, but that might fail your delivery, so use with testing and caution.