Because it is not relevant. B-theory time and A-theory time are not related like an affine space is related to a vector space. You can't get from B-theory time to A-theory time by picking an origin and calling it "the present". The whole point of the A-theory is that the present is not a static point in time. It moves. The particular mathematical representation you suggest doesn't capture this.
Right, I was pondering that, too:
A-series (non-affine) "is past", "is present" and "is future." Here there is a fixed (for a given time) origin.
Indeed the transformation does not capture this apparently moving origin. What does "moving" mean in this context? How would you describe it mathematically? In the block universe model, this is ought to be pretty easy by introducing a shifting origin, but it is probably harder in the growing block universe model. I need to think about it some more, feel free to point me ...
Despite being (IMO) a philosophy blog, many Less Wrongers tend to disparage mainstream philosophy and emphasize the divergence between our beliefs and theirs. But, how different are we really? My intention with this post is to quantify this difference.
The questions I will post as comments to this article are from the 2009 PhilPapers Survey. If you answer "other" on any of the questions, then please reply to that comment in order to elaborate your answer. Later, I'll post another article comparing the answers I obtain from Less Wrongers with those given by the professional philosophers. This should give us some indication about the differences in belief between Less Wrong and mainstream philosophy.
Glossary
analytic-synthetic distinction, A-theory and B-theory, atheism, compatibilism, consequentialism, contextualism, correspondence theory of truth, deontology, egalitarianism, empiricism, Humeanism, libertarianism, mental content externalism, moral realism, moral motivation internalism and externalism, naturalism, nominalism, Newcomb's problem, physicalism, Platonism, rationalism, relativism, scientific realism, trolley problem, theism, virtue ethics
Note
Thanks pragmatist, for attaching short (mostly accurate) descriptions of the philosophical positions under the poll comments.
Post Script
The polls stopped rendering correctly after the migration to LW 2.0, but the raw data can be found in this repo.