Why would anyone make a replicant?

[Stark]

The whole thing (and why everyone including Scott and Ford hate it) is because it sets up that 'happy ending'. Sure it might be true and I don't see why not, since Rachel has no special powers and so why wouldn't she live longer, but this doesn't mean they can make a guy like Roy live for longer.

Even if they wanted to, which I think they probably don't.

[Guardsman Bass]

I think I prefer the lack of it, too. Having both Replicant Deckard and Replicant Rachael on the run with only their four years (of which they've used an unknown amount of time) represents them doing what Roy couldn't do: reveling in their time on the run instead of dreading death and fighting a futile battle to avoid it.

[Stark]

Yeah, its them living their own lives for whatever their time is (and as Adama says, nobody knows how much time they get, so they should value each moment) rather than living as a dead man like the population of Earth or living as a slave like replicants in the colonies. They've seized the day.