Hi,
I don't think it can be considered bizarre. I wonder if you perhaps compare it to something like Google Drive or similar, where you store documents and each document can have their own version history but when you fully delete a document, it is gone, including all versions of it.
But Subversion, and indeed other version control systems, are designed for different use cases. Almost always the files are related to each other and an important use case is to look at how all the files appeared together a week or a year ago. It doesn't make sense to delete a single file and all old versions of it, because then looking at history would not show a complete picture. If the files were source code, the old version would no longer compile.
Different version control systems might offer various features to actually rewrite history, but doing so is normally considered special case functionality, used only in special circumstances and not part of normal operations.