I think the Maya participated in the invention of writing much earlier than thought. As cities began in Mesoamerica around this time, writing was a part of that, just like public art and presentation of political ideology. It's all part of a package.

Currently the policy is to acquire them on a voluntary basis, there is also an issue of cost.

It's like trying to read some of the writing in medieval manuscripts or handwriting from the 1500s. Even though it is our same writing system we don't recognize it.