I’m not sure what to make of that, can you clarify what you mean? To me it could mean any one of:
1.“I don’t think the REPL is useful” (and therefore neither is this guide)
2. “I’d like to know why the REPL is useful”: there’s a paragraph about that in the introduction, can I improve it?
3. “I’m don’t have much experience with the REPL”, in which case thank you for the clarification.
About everything that you see in this guide, I use in my everyday work. Some of it you may not need, but if I leave it out, it will take much more effort for people to discover it on their own than to skim through a boring paragraph 
- The CLI tools are not available everywhere (e.g windows)
- People may join or have existing projects using Boot
- I’m being consistent with the getting started guide.