Obviously, in a perfect world they'd have all parts of the system in place and ready to go at launch, but they're not going to be able to do that.
There are more benefits to at least have building aspects in place at launch than leaving the whole thing out until it's all done.
Being able to move out away from towns with your group, regardless of size, is going to be pretty important for this game, especially initially, the towns as they are just cannot support the whole player base, at a technical level and in terms of quality of game life.
Building houses and keeps also provide an important goal for groups and individuals to strive for alongside and following skilling up your character and building wealth etc. While it does take time to develop your character and get some resources...it does not take much time, especially if you played the first game, played this beta quite a bit, or are just part of an organized group, and people need to have that next greater goal to work towards else they lose interest, quit, or sometimes just begin to cannibalize the player base because they haven't much else to do.
The freedom this game provides is incredibly important, the freedom to build and destroy, no doubt about it, but they are not exactly equivalent.
There are some here that do not understand that, or just reject it out of hand because "But my Freedoms!!!", but it is more important to the greater player base to be able to go out and build than it is to destroy everything. Both are important long-term though, absolutely.
Again, I don't get the problem with putting in the building before the sieging is ready, and without the whole TC system a rival guild in a keep in a region you want for yourselves or whatever is not game changing because they can't influence that area outside of existing in it.
And furthermore, if you can't build up the current existing keep locations, there is no reason to even be at or near those locations whatsoever, so those parts of the map will just be more empty spaces in the middle of the wilderness with no purpose, which this game currently has an overabundance of if you haven't been paying attention.
At least this way, even if you can't siege it down on day 1 and make grown men cry, you can still go there and find PvP because people will actually live there, meaning players coming and going and building and developing near those locations.
To say that a great nothingness is better than having large amounts of players moving out and developing and inhabiting all the open and empty spaces on the map, only because you personally can't immediately destroy them, is probably one of the dumber arguments I've seen made on these forums, and there's been a lot of dumb arguments and suggestions made here lets be real.
In the end, and this is just my opinion obviously, this comes across as certain people realizing someone else is going to get something they want before they do, and mommy always told them they were a very special little boy who gets to have everything he wants at all times, society be damned....and they can't abide it, and so they go out and scream about the sky falling in a sweat induced hyperbolic rant, but the sky isn't falling, and overstating your case won't make it so.
Both of the arguments made on both sides are wrong tho. The larger clans will claim the keeps fairly quickly, thinking they won't is weird to me...more people = more gold and resources collectively, that's pretty basic, but it obviously won't be as fast as it was in the beta because everyone will start from scratch, more than half the clans that currently hold keeps won't have them again after launch I don't think.
The real thing we should all be worrying about is that once sieging is in game that it won't be an option for all. Early on in MO Siege equipment plans and the boulders and ammunition needed for them were available on vendors in towns. This made it so that anyone with enough resources, numbers, and organization could challenge another groups claim, this was good and not imbalanced because if a keep owning clan pissed someone off those players had recourse to do something about it. Later on tho they removed those vendors and made siege only available from the keeps themselves, which meant that those who held keeps controlled access to siege, and so out of self interest and worry about being sieged themselves, those clans would nearly never sell siege to that new up and coming group who had the numbers, the energy, the gold, and the desire stir things up. They were told to go gather boulders off the ground....very few had the determination to do that obviously, and it sucked.
Eventually things evolved and with the later incarnations of TC you could build a stone cutter for boulders...but this came long after the previous system created utterly boring stagnation on the server. The question then becomes which type of system are we getting? Most likely more in line with later TC, but whatever the case they hopefully don't lock sieging ability behind some arbitrary wall that locks the underdogs out of that aspect of the game.