Realistically a continuous edge is better as weapon. Thus the starting point should be thinking about the drawbacks of a normal edge that a serrated edge doesn't have and under which circumstances they would be relevant.
Amount of metal
Before metal working people made weapons using microliths. This means attaching small pieces of stone worked to have a suitable edge to properly shaped piece of wood to form a weapon that is larger and more massive than can be directly made from the brittle stone and with sharper edge than wood can hold.
The stereotypical example is Aztec macautl, which used its large mass to make the edge effective in combat and allowed users to replace broken obsidian blades without replacing the whole weapon. This made sense since Aztecs didn't have a non-brittle material to make large weapons from. I expect they could have made copper maces, if they had wanted to, though.
So if your "cutting edge" material is expensive or brittle (or otherwise has limited endurance), you might want to use this construction and naturally end up with a serrated edge. Similar factors do apply to improvised weapons.
This is not sufficient to answer your question by itself, but should be added in as a factor to give some depth and historical background. Details like this make settings feel richer.
You don't need the weapon to be efficient
Armor penetration is not important if your expected opponents do not wear armor. Historically people had different weapons for use during wars against soldiers with armor and during peace against people wearing normal clothing. The latter category then further split to have different weapons to be carried for self-defense and for use in formal situations such as duels and sport.
So the first constraint would be that it probably isn't a military weapon. And more probably it isn't self-defense weapon either as such should be simple and efficient. A self-defense weapon that needs extra maintenance or fiddling so that you never quite keep it in top shape is a bad thing. That leaves formalized combat in duelling or sports. The line between the two is not always clear.
In such formalized combat leaving large messy cuts that are clearly visible to spectators, scar messily and hurt a lot would be beneficial. At the same time single hit kills or maiming is not really desired. A serrated edge can be built so that it cuts efficiently if messily to certain depth but then essentially becomes a blunt edge when cut depth exceeds the height of the teeth. Further you can easily cover the serrated edge with "antiseptic" material that ensures the cuts visibly scar and hurt enough to incapacitate recipient, but are unlikely to get infected.
This may seem unlikely, but the Aztecs mentioned earlier mostly warred to get captives to sacrifice to their god. Such wars were formalized enough for both sides to accept a less practical weapon that gets prisoners instead of casualties. Similarly Roman gladiators started as a religious ritual and gradually transformed to entertainment. They successfully used lots of "impractical" weapons. And not only was watching gladiators massively popular, people actually voluntarily participated in the training and even matches. In Germany they had an academic sport based on cutting each other in the face with a blade that makes shallow cuts. Such duelling scars were then a mark of honor to the bearer. A more full-body version could use a serrated blade.
In all cases you should include the historical connection to the microlithic weapon construction mentioned before to explain why this particular weapon is the proper traditional one that honors the gods and ancestors.