Should I ask my students to contribute in preparation of the manuscripts?
When I did my masters, I had this problem. My old supervisor ended up rewriting a paper from scratch. He never really gave me any feedback except that my writing of the paper was not good and there is no way it will be accepted. I now understand that this approach was a waste of his time and a waste of a learning experience for me. 

Now I am working with a different supervisor and when I write a paper, I get a lot of comments and feedback and we end up doing 4-5 rounds or review. I think the initial draft is usually not good. But after all these rounds of review, I end up writing a "good" paper myself. 

Maybe your students need to realize that they have a problem that THEY need to address. You writing the papers on their behalf does not solve this problem. Initially, push them to write a draft regardless of quality. Then do rigorous review afterward. With time, their writing will definitely improve