Why is "Force GPU rendering" disabled by default Developer options?

Why is this feature disabled? When I turn it on, many apps and become snappy and awesome with smooth graphics. Seems like it'd be nice if it was enabled by default. The linked article in [this question](https://android.stackexchange.com/questions/17731/force-gpu-rendering-in-ics-how-does-this-affect-system-performance) says that hardware acceleration wasn't default up until 4.0. Is the "Force GPU rendering" option then targeting apps that use API for 3.0 and lower?