ELI5: How come very simple app updates are hundreds of MB in size?

I have here today on my update list: a VERY basic game called block blast (as complex as Tetris, at most), a Documents (PDF etc) file manager that all it does is store and opens these files on an iPhone, Express VPN which is also a quite simple and mature software.

All these apps are years old and I'm having to download upwards of 200-300MB just for an UPDATE.

How come they are so big for something so simple? These updates are all bigger than Windows 98, a complete Operational System with an incredible number of functionalities and much more complex.