Why? Hardware and software architectures often have radically different needs from their loader, it doesn't make sense to have one format to rule them all. And

Why? Hardware and software architectures often have radically different needs from their loader, it doesn't make sense to have one format to rule them all. And any format flexible enough to support all use cases would just be a container for other formats, and in practice, loaders would ignore the variants that they don't/can't support so developers would need to care about porting things anyway. ELF is pretty stable across many architectures and platforms but it's proven to be inflexible enough for plenty of applications where people develop their own, or alter it in varying ways.