There are many theories why Monsteras have holes and splits in their leaves (technical term is leaf fenestration). This is a very interesting one.
Monsteras are native to lush tropical rainforests in South Africa and grow from the forest floor, climbing and vining their way up trees to reach as much light as possible. Since rainforests are so dense, the smaller understory plants can only survive by capturing the small amounts of sunlight that break through the canopy.
To capture as much of it as possible, Monsteras produce large leaves as they vine up trees towards the light. When they do this, the larger leaves eclipse the lower leaves of the plant, leaving them completely in the dark. This lowers the amount of light that can be absorbed by the plant as fewer leaves are getting light. The more leaves that can catch some light, the better! To get around this problem the leaves develop fenestrations so that the light can get to the lower foliage too which increases the total surface area of the plant that can receive sunlight. The plant soaks up as much of the sunlight as it can, helping to keep it happy and healthy.
I love this explanation because it shows how resilient they are. They were living in difficult conditions, had a problem, figured out a solution and adapted to its conditions. Then it got on with growing! It kind of reminds me of what we're going through in this 'new normal' COVID era and how we basically have to do the same thing. Adapt and grow