The way it is is really how we all want it. 86400 seconds = 1 day. And we operate under the assumption that midnight UTC is always a multiple of 86400.
We don’t want every piece of software to start hardcoding leap second introductions and handling smears and requiring a way to update it within a month when a new leap second is introduced.
You never worried or thought about it before, and you don’t need to! It’s done in the right way.