Actually Helgen repopulates with bandits after you've been out of it for a while... I went back there once just to see and it was filled with enemies...

But why is it that other cities and towns dont do the same as Helgen did?

Because the destruction of Helgen was a plot point. It was written out from beginning to end, and rather than leave it permanently empty, they threw in some random bandits. Your indiscriminate slaughter of innocent townsfolk, on the other hand, is not a plot point, and there's no reason for Bethesda to try to anticipate it or work around it.

Besides which, there was never anything you could do in Helgen anyway. No inns, no shopkeepers, nothing. Just a bunch of people scripted to die in the dragon attack. The bandits don't really replace anything.

Well this is where I disagree, Because I think bathesda knew that dragons would attack towns such as riverwood in my game where tons of people have been slaughtered by dragons. I have not taken the time to wait 2 in game months to see if anyone comes. Anyway they must have anticipated that, and since the blacksmiths and job givers are dead that town is useless now....

To be honest, there is no dev note or dev announcmenet saying NPCs do not respawn in towns.... So I am optimistic until that happens..

Sorry, it's not going to happen. This really is just a limitation of the way they make NPCs and what happens when they get attacked by a fire-breathing monster. Even with Helgen, the NPCs it replaces them with aren't proper NPCs, they're generic bandits who do nothing but attack you.

They let you live with your actions. Like the example in morrowind, if you are to kill a major npc, you would get the "you must reload or live in your doomed world" message. They wouldn't respawn them, or restart your game for you, it was your choice to do it and live with the consequences. Its the same in skyrim, though without the message, since really essential npcs are unkillable.

Helgen was most likely programmed like a fort or cave so that it would respawn bandits...theres no shops to visit or homes in the city so theres nothing to program like pathing and routines and it wouldn't be a problem adding in some bandits automatically by the game. Cities are different and are designed to hold npc's and shops and will have individual pathing and routines programmed into them....cities do not just randomly generate and program these things and you wont be seeing repopulated towns because of this.

I am not saying for instance if you kill belethor the shop keeper in whiterun, that he should respawn... That would be pointless.. I am saying maybe another merchant who comes to the city looking for opportunity uses the store instead...

Another example of what I am saying is: If you slaughter everyone in rorricksted you then cant do a lot of the little quests right? Well instead of all those people respawning, have new people that are some what generic come into town and live there and the diologe you have with them is very minimal meaning the quests from the dead npcs that were slaughtered are gone as well. If that makes a little sense. I would think there would be people on the roads who move into cities.... I have seen sometimes in town inns and citie pubs some generic ork or redguard characters Just enjyong some meed with the locals.... so it is possible I am sure...

If they kept them generic and basic name npc's that could repopulate im sure it could be implemented, but that takes away from any of the little attachment one may get to specific npc's taking away from immersion. Sure they can go ahead and repopulate the towns with less involved mindless npc's but eventually it will be the same as living in an empty town and you just wont care that they are there. I don't think they would implement anything more complicated then an npc named redguard or orc with slim rehashed dialogue and some sort of pathing and schedules so I would not hope for this in the current game. I would predict this hopefully in the next installment, as long as its done right, with attention to detail, not rehashed npc's over and over again with no personality like the original named npc's had.

I agree with you totally. Hopefully with the next eldar scrolls and the advancement in game making technology, they can create some sort of repopulating system that creates great mindful NPCs to repopulate towns that have been sluaghtered

Does this even really matter? I mean, if towns did repopulate after a set time then the op will just kill them all again away.

People are much more valuable alive.

i dunno, i killed "the skinner" guy (silver hand hideout leader) more than once. the first time during companions questline, and the second time he magically resurected himself along with every silverhand bandit in the cave during another random bounty quest.

Someone on the UESP agrees. He is classified as a Radiant NPC, but has been found respawned after the fact. Could be a bug.