The Standard Course workbooks carry two things the textbooks do not: a full 模拟试卷 model test in the appendix of every level, and — at HSK 5 — the listening transcript and answer key for every workbook lesson. Those are collected here, scanned exactly as printed.
The per-lesson exercises stay in the paper workbook — they are write-in pages and there is nothing to gain from photographing 900 of them. What is worth having on a phone is what you cannot do without the book in front of you: the model tests, and the HSK 5 transcripts and keys. Levels 1–4 print no key for their model test; that is the publisher's choice, not an omission here.