So why not on current bike(s)?
Because it's more to add to the specification of bicycles, because in the dog-eat-dog world of chain lube formations an automatic or semi-automatic lubrication device is seen as unnecessary, and because it doesn't offer great advantages over a bottle of lube to those who cycle only in good weather, and arguably is of less benefit to recumbent bikes whose chains are generally less exposed to the road and front wheel rooster tails.
But for regular riding in bad weather, or indeed when bad weather turns to good weather and your chain has been soaked in rain and grime, then baked dry by the sun, it's a good accessory. Although you could carry a bottle of lube in a saddle pack for example, it's an installed system that requires only a squeeze of the dispenser squid.