It's been a long time but from what I remember the selling point for EASTL is the ability to specify your own allocator instance for every container. EA writes portable code across lots of different architectures, many of which share a lot more with embedded systems than with PCs. They have constrained memory or special dedicated memory areas. Also, iirc EA uses tagging allocators extensively letting them trace against memory budgets down to the team level.

Edit: there's an extensive FAQ in the docs folder: https://github.com/electronicarts/EASTL/blob/master/doc/FAQ....