First, if you are interested in scientific research in the future (of course, it is unlikely), then the importance of English goes without saying. The textbooks and papers that you are most likely to contact and be familiar with are written in English (of course, if you are studying in Russia, France and Germany, I am talking nonsense).
Second, even if you don't engage in this major after graduation, you should think about what kind of job you want to engage in. This job requires high English. This determines whether you want to take CET-4 or CET-6.
Thirdly, I personally think that CET-4 and CET-6 are proof that my English is OK when you are looking for a job. At least I have the ability to further study and master the English knowledge that needs to be familiar at work. Of course, I'm not hiring. I really don't know what others think of CET4 and CET6.
In my personal opinion, CET-4 and CET-6 are easy to pass, and there is nothing to say. It's not easy to get a high score, but it doesn't prove that your English level is high, because there are always deviations in the exam, which can only prove that you did well in the exam. For example, if CET-4 and CET-6 don't take the oral exam, I will recruit people to ask employees to communicate with others in English. So even if you pass CET-4 and CET-6, can you guarantee that you can communicate with others in English?