I tried some honey I got at a farmer's market and noticed it was really thick compared to regular honey you buy at any supermarket. 
This should be a comment but I am not yet able to do so.  My neighbour is a beekeeper and I asked him the same thing yesterday. The reason why (or rather when) honey crystallises or not is because of the ratio of glucose to fructose. The former tends to crystallise, the latter not so much, but in general every honey crystallises when left alone. Now as Chris already said, most commercial honey is heated to keep it fluid and more appealing (to some).  Acacia honey for example stays fluid for long periods of time even without heating, because of the high fructose content (but you can't really tell bees where to go, so no honey, whether from this or that flower, is 'pure').  There is also a honey that's really creamy, with a texture similar to Nutella. This is the result of stirring the honey continuously during the crystallisation process. This breaks up the bigger crystals into smaller ones which are submerged in the liquid part. Stirring also creates tiny air bubbles further contributing to the creamy texture.  Everything I wrote is only true for raw, unheated honey. I have no idea how creamy honey is made commercially, or how the productions differs. 