Because the year is 2000-2002 and you are embarking on writing a game engine targeting PC, Mac, Xbox, Playstation, and any other consoles or platforms that come onto the market before your engine is finished. Compilers and standards compliance was a shit show. Things like EA-STL might look silly nowadays, but there are many great reasons why companies rolled their own stuff back in the day.

Even now STL is not perfect for realtime and threaded programming.

Thus comes from outdated and schizophrenic approach to memory management. It is getting fixed but that will take years and multiple revisions of standard.

Let's start with lack of immutable objects, continue with missing support for pmr or allocators and finish with hidden default heap allocations in algorithms and data structures. (Including some smart pointers.)

#schooled