Source games will probably always have it. Dark Souls is not surprising, since they are meant primarily for console where LAN gaming is rare. And what an annoying move by Blizzard for Overwatch.
The trend is not unlike the trend to restrict dedicated servers to paid rentals, like what Battlefield 1 does. This is even more atrocious if anything, and as with the dropped LAN support it's a trend seen on console focused titles.
EA went even further with BF1. They dropped support for third-party hosting companies and server management software like ProCon. Now the seervers can be rented from EA only and server admins cannot manage the servers remotely and run custom scripts (such as auto-kick).