I don't remember ever saying that. Whether some Service Sims can ever successfully route to where they need to go to perform their services may be a different question, but I've never played a world with no roads.
You cannot have a world without Service Sims. Immigration is all about resident households, not homeless NPCs. You can instruct NRaas Register to stop using what it calls "immigrants" which in that case means new, specially generated sims to take up role object slots. but those are Role Sims, not Service Sims, and then you will need to either have enough residents to fill those role slots or else not have any role giving objects in town at all. And on top of Service Sims, the game itself will generate homeless sims to fill career slots if there aren't enough residents in town to provide bosses and co-workers, plus homeless street performers if Showtime is in play. None of these are controlled by resident immigration.
