Why do people want Helgen rebuilt.
I dont see why it should be.

It should stay as a ruin for 4 reasons-
1) Alduin destroyed it.
2) Ulfric Stormcloak and Dovahkiin would have been executed if Alduin never attacked.
3) The civil war would have basically finnished if Ulfric was executed.
4) It should be left as a memory of the above reasons.

The game has tiny cities and villages with barely anything to them. It is natural to want more of these cities and villages. Here we have a perfectly good spot for a village that's already built, but its destroyed.

Honestly, it was an important trade route, thats pretty much why. Also, things like that, should be rebuilt over time, like Kvatch in Oblivion, when your character has been adventuring for years, there should be some option to rebuild.

I think most people don't really care about Helgen. They just want a fort-like place they can rebuild and govern.

I dont think that points have really something to do with the reconstruction of place after its destruction, no matter the cause.
In this case, the only real reason that came to my mind is that people in Skyrim are so worried (ever if in game they dont really demonstrate it) about the dragon attacks and the scourge of the civil war, that the resources and time to rebuild it are just not available.
Considering the city is in a crossroad that goes from Witherun - Falkreath to the Rift, it seems to me as an important node. I see more reasons for the people in Skyrim to want tit secure and at least occupied by guards than left in ruins as home of bandits, make the passage trough the zone very dangerous.

I dont see the point in owning a fort. Hearthfire houses are good enough.

Houses =/= Fort or Stronghold

I like that Kvatch was never rebuilt in a DLC. it is probably rebuilt now though.

the houses have all you need. why would you want a fort.

For the players that like the more military approach and no the "family and children" one.
In a fort you have walls, all that martial feeling, guards, etc.
Its just a different environment, very different of the nice house in the woods.

I see what you mean. I would use a fort if roleplaying a bandit but not Helgen.

Yes, its just an alternative option for people that dont just want a house.
In my case, I found fortunately a mod that add some walls to Lakeview, and the chance of hire guards on it, very well done.
And I also modded it a little to make them all dunmer carved in bonemold... and now I feel like I really have a good house

Why not have the opportunity to lay waste Windhelm or Solitude instead, including salting the earth so that nothing ever grows there?

For long term rp, seeing Helgen rebuilt creates a sense of achievement and moving forward.

Give me a military stronghold in Winterhold!

Well, they did the Kvatch Rebuilt mod for Oblivion... I can see it coming for Helgen in time

Agreed.

a Helgen Rebuilt Mod would probably be made already.

Hmm no, I think they did not manage yet to do it.
Im always exploring Nexus and the Workshop for new things to add
I mean, a project could be on the way, but nothing complete or of good quality yet.

A rebuilt Helgen mod is likely much more complicated than the Oblivion Rebuilt Kvatch mod. Many important scripts that start the game are tied to Helgen. A rebuilt Helgen mod would be a much more tedious and delicate undertaking than its Oblivion counterpart.