And that's also a good defensive move.

Given the market is moving, even IBM's major customers would eventually migrate to newer technologies. (On the order of decades)

By providing something that mostly satisfies that need, IBM essentially drilled a relief well to take the pressure off. When they're ready to migrate, they could get 80% value of what a non-IBM migration would get them by moving to IBM's product.

For a lot of large, slow, conservative orgs, that's good enough.