Why return packer.startup()?

[ZachariahTheMagnificent]

The readme specifies that you write return packer.startup(). From what I understand, this exports whatever startup() returns for use outside the lua module. This doesn't seem required as far as I'm aware and I'm confused as to what this is supposed to do. What is startup() returning that we want to export out?

[dyllandry]

I have the same question.
I found places in the help files that don't return:

USING A FLOATING WINDOW                        *packer-floating-window*
You can configure Packer to use a floating window for command outputs by
passing a utility function to `packer`'s config: >lua

  packer.startup({function()
    -- Your plugins here
  end,
  config = {
    display = {
      open_fn = require('packer.util').float,
    }
  }})
<
By default, this floating window will show doubled borders. If you want to
customize the window appearance, you can pass a configuration to `float`,
which is the same configuration that would be passed to |nvim_open_win|: >lua

  packer.startup({function()
    -- Your plugins here
  end,
  config = {
    display = {
      open_fn = function()
        return require('packer.util').float({ border = 'single' })
      end
    }
  }})
<