Why doesn't acacia honey crystallize?
The crystallising of honey depends on the amount of glucose (sugar) you have in the honey. Crystallisation occurs in solutions that are (like honey) oversaturated with sugars. Less saturation means less likelihood for crystallisation while water presence affects the distribution and size of crystals. 

In terms of moisture you have two types of crystallisation:


If moisture exceeds ~14% large crystals form at the bottom of the container and the honey seems otherwise OK. That is indicative of moisture excess in the honey which is considered of inferior quality. 
If moisture is less than that, the honey crystallises uniformly. That is a normal phenomenon.


Now aside from the way it crystallises, depending on the glucose content you have faster or slower times for its crystallisation. The lengths I quote refer to Mediterranean (Greek) climates. In Scotland, every honey I've ever brought from Greece apart from fir honey has crystallised within weeks. So in terms of glucose:


A high glycose content of ~40% would have the honey crystallise within 2 months from harvest
A moderately high glucose content of ~35% would take 6 months to a year to crystallise
A honey with normal glucose content of ~30% would take a couple of years, and
A honey with low glucose content &lt;30% would not have enough sugars to crystallise (that's my fir honey and my honey of choice)


My reference is a website about honey (in Greek) cross-referenced with the answer I got from a producer when I had the same question.

So to answer your question, your honey doesn't have enough sugar to crystallise. 

But even if it does, worry not. Bain-Marie (don't microwave!) it for 1/2 an hour and the sugar will melt its way back into its uniform honey goodness.