<facepalm>
It isn’t simply economic. I don’t think you understand the fundamental purpose of an energy grid.
It isn’t just a bunch of wires existing on their own. It is the energy delivery infrastructure for all of society.
“Baseload” is an attribute of the grid itself that indicates the minimum energy capacity these wires at present carry.
Baseload is NOT a constant value or a constant consumption pattern across time of day/day of week alone.
Baseload reflects the consumption of energy by society that the grid is DESIGNED to serve at any time.
In other words, were one to use your definition, the grid would no longer be considered a functioning grid anymore but one that is broken since it is incapable of meeting its minimum design specifications.