Designing the satellites to self de-orbit would be massively more efficient, but this technology is being developed to de-orbit older sats and other debris without that capability. It could also be useful to remove satellites that fail or who's de-orbit system fails. There was a recent test of a grapple system that harpoons a target sat, but it's early days in the development of such systems for arbitrary sats, rather than recovery missions designed for a particular target sat.