At first glance this might seem an extravagance, but at any one time there must be one or more spacecraft that are closely enough aligned with the Sun, from Earth’s perspective, to make direct line of sight comms suboptimal or even risky.

On further inquiry, it seems that some studies have been made, but no actual projects are underway. Curiously, studies of “target” planet relays, around Mars for example, have attracted more interest than Earth-based relays using (say) Earth’s Lagrange points.

But at first glance, it would seem to me that Earth-based relays would service more potential targets, and do so while adding the least additional comms path length!