Hi,
Can tank run without a skimmer? Of course. With well knowladge, lightly loaded, lightly feeding, lots of biological filtration and keep close eye on your tank. It can be done very well. But if tanks biological filtration overloaded it will fail then your tank will start having problems. This point skimmer starts to work.
If big fish dies in your tank without your knowladge it will cause lots of problems. Skimmer helps to clear that mess up before it damages more.
So it has positive points
But again its my opinion
Burc