Ever wanted to print a lot of objects, in different filaments, but not spend forever changing every layer?
You might reach for print-by-object, and then run into this problem: too many objects to fit on your plate with all the room they need to not get hit by the toolhead.
Get your objects that are the same filament and merge them.
This gives you one object per filament, drastically reducing the number of filament swaps you need to do when you enable print by object.
This can be especially useful if one of your filaments is stringy, like PETG or TPU.