Under what circumstances would this change be useful?

When I have a bunch of custom cells and my graphics designer says "Can you add another table just like that one with another data set that doesn't have a header?"

How would you know which column is which field then?

I had a similar need, just slightly different. Currently, the Grid assumes the header is in the same table as the Grid. In my case, I needed to place the header in a different table that was in a fixed position, the traditional header lock layout. The default grid render would append the header, so I overrode it not to do that, instead I passed in the header_element as an option, and had it use that when initializing the header, and skipped the appending.

something like: !this.options.header_element && this.$el.append(this.header.el)

@wyuenho I have a similar scenario to @kriswill - I need a fixed header (which I intent to achieve with a disparate table), and I also have a second set of data in the same format that needs to be grouped separate from the first set of data. EG:

Object - The Thing
Collection - The Collection of The Things

Collection1 - A subset of The Collection
Collection2 - Another subset of The Collection

Table 1 - Floating header, no data.
Table 2 - Collection 1, no header
Table 3 - Collection 2, no header

From that point I intend to listen to sort events on Table 1 and funnel them into Tables 2 and 3 - allowing them to remain sorted per user preference, and still separate

I couldn't find someone who solve this problem, so I made a plugin who works with backgrid to manage fixed header.

https://github.com/gsantome/backgrid.fixedheader

In my project is working GREAT and it's really easy to implement.