I think one of the biggest reasons why people talk about the scene is because we don't really get a payoff for it. Thorin tells Bilbo to go home and plant his tree, but we never see the hobbit do that. We want to know what became of the acorn since it tugged at our heartstrings so much.
Popular belief for a little while was that the oak tree on top of Bag End was the tree that Bilbo planted from it. However, the few exterior shots that we see of his house in the beginning of An Unexpected Journey and the end of The Battle of the Five Armies seem to show that the tree was already there prior to his adventure.
I tried comparing those shots with shots of Bag End from The Fellowship of the Ring to see if any other trees had appeared there since the Hobbit movies. There's one lighter colored tree on the side of the hill in Fellowship that looks small enough to have been planted fairly recently, but it's hard to tell from the angle in Battle if it's already there or not. In any case, it doesn't look like an oak tree.
This left me in a bit of a quandary. Was I overlooking something? Was the acorn scene such a last-minute idea for the Hobbit movies that the filmmakers didn't have time to go back and remove one of the trees from Bag End's exterior shots? Was there a deleted scene showing where Bilbo planted the acorn? These questions were nagging me so much one day that I decided to research the matter using one of the greatest sources of information known to modern man.
And sure enough, I found an answer. Apparently, there is going to be a bonus scene in the Battle of the Five Armies Extended Edition that shows Bilbo planting his acorn—in Dale.
This of course raises all sorts of new questions. Why would Bilbo do that when Thorin told him to plant the tree at his home? Did Bilbo not want to remember his journey after all? Did he do it to leave a reminder of himself in the closest place to Erebor where a tree could grow?
My personal theory is that Bilbo knew by then that Bag End was never really going to be his home anymore, so he didn't want to plant his tree there. Maybe a part of him always knew that he was going to leave the Shire again one day and try to return to Erebor, so he saw the East as his home instead. It would certainly lend a more poignant subtext to his decision to leave in Lord of the Rings; one of his motivations could have been that he wanted to see his oak tree once before he died.
As most of my essays these days end though, no conclusions can really be drawn until the Extended Edition comes out. If there is a scene of Bilbo planting his acorn in Dale, it could contain dialogue or something else that conveys his reasoning. It's also entirely possible that it won't, and that the reasoning will be left up to the viewer's imagination. Either way, I suspect that Bilbo's acorn and the tree that grew from it will remain a popular topic of discussion among Hobbit fans after this November.