I try to avoid any specific recommendations of services because everybody's needs and priorities are so wildly different. I'm very much of the belief that it's best for people to take a look themselves rather than rely on others' preferences.

In terms of not mentioning other services, it's probably more a matter of the book being in progress. I've done quite a bit of research, but the vendors list is rather incomplete because I'll be including it in the appendix of the book. So in most cases it's simply a matter of the fact that I haven't actually finished it yet. These are mainly just from my notes that I've jotted down.