They need to be able to correct grammar mistakes and understand what English speakers are saying to get a good score on the exam for most universities. You do not need to write sentences or actually speak English on the exam. Consequently students do not focus on writing or speaking. Who can blame them?
Students study English for at least 9 years. For many of those years they study everyday. Most can barely write a sentence or utter a few words. Writing is easier than speaking. How am I supposed to teach conversation classes if the students can not write a sentence? Last night I was up for hours worrying about this.
If the goal is for the students to communicate in English (why study English if it is not), then the testing system is set up to fail them. It really is too bad because the kids are really smart and capable of much more.