为什么OpenGL ES函数不能从另一个线程调用?

I am experimenting with writing a small game engine for Android using OpenGL ES. I have created a Game Thread which updates the game objects and the GLThread with draws the scene. I had read that you need to load the textures in onSurfaceCreated method of GLSurfaceView. I am following that but for some debugging purpose I was trying to load textures from my Game Thread instead of the GLThread. I got no errors and the texture were not showing up on the screen. I spent my entire day trying to figure out the problem and finally I read the below I am experimenting with writing a small game en