I agree with Sorce that a /lot/ of things /can/ be rooted in water. Transferring them over to soil takes an interlude of very wet, boggy soil at least for a week (or several for slower growers) to give the roots time to shift over and adjust to drier soil, and then perhaps another transition to course macro particulate media. So if you can root it in media other than water first, you can skip some of that difficult transition time that causes people to loose a lot of plants. The faster such cuttings root the faster and easier the transition. Those that are really slow or have very brittle roots are much easier to loose.
Beginning in perlite or spaghnum moss, or even damp sharp sand, will often give you better results faster than water. And in chilly winter or early spring weather starting cuttings on a heating mat (and domed for high humidity) also help a lot. Even standing in water, if you have low humidity your cuttings may dry out more rapidly than they can take up moisture. Watch out for fungus on top and bacterial rot below. /Some/ cuttings are easier to start in a cold frame without a heating mat. Some will need rooting hormone and others won't. Bright light is generally necessary but in some cases it isn't. Do internet searches to see what works best with each variety you want to try.
That said, I have started a number of things in water over the past 45+ years. Euonymus (burning bush), crab apple, some kinds of hibiscus, spirea, some Japanese quince, ivy, wisteria, ficus, etc. I do find adding willow cuttings can produce better results if you are working with something that's a little difficult to root but it's no guarantee. That's my two cents - your mileage may vary with your growing conditions.
