In some cases, those cards might not even cover the processing cost
You want to mill opponents to get access to their creatures or artifacts, and you can keep attacking people with horrors to mill even more cards
If you want to use 10-cost Five Elders on the same turn, we need The Empty Throne in the list, which we can play for free at the start of the turn
Luckily, there are a lot of different permanents that have the same function, so even if one gets removed, you can draw into a different one.
The saving grace for all these cards is that they can always be cast for 1 mana to secure your next land drop, making them great early on without being embarrassing later
Considering the myriad options you have for returning cards from your graveyard to play, you should treat this Golgari sorcery as just plain better than Shared Summons, even if creatures in your graveyard are a little more vulnerable than the ones in your hand