"MAME is a multi-purpose emulation framework."

These systems still run custom hardware for things like IO, and those parts of the systems are emulate-able.

Getting emulation of said IO chips and whatever seems pretty inline with MAME's mission statement: "MAME's purpose is to preserve decades of software history."

Mame is a platform to keep old games playable on modern open hardware.

Emulation is an implementation detail. It may be the best approach or it may be abstracted away.