I provided all of my letter writers with my CV, copies of my SOPs, two writing samples, a list of programs with the POIs and explanations for why I wanted to work with these people, transcripts, and copies of my teaching evaluations. An applicant can always provide information to letter writers without personally writing the letter.
During my UG and MA I've solicited letters from about 10 separate individuals for applications/scholarships/grants. None have ever asked me to write my own LOR. All of the people that I've spoken with find this concept unacceptable. Often times it is precisely because the recommender doesn't want to spend the time or simply doesn't know the applicant. If it is a matter of knowing the research of the applicant, this information - most of which ought to be included in the prospectus/proposal - can be given to them. Providing such materials is MUCH different from personally writing the letter.
Nevertheless, it places the applicant in a terrible position to comment on their own performance. I would hate to try to do this for myself, so I'm glad that no one has requested it of me. Upon soliciting the LOR I always mention that I will provide a folder containing the aforementioned materials (or any others of relevance). If I were still asked to write it myself I would give strong consideration to finding a different letter writer. But, if I had no one else, or if they were a potentially strong LOR, I would certainly write my own letter. But I wouldn't be thrilled about it.
If I'm ever a prof, I hope I don't ever ask a student to write their own letter. I feel it defeats the purpose.