I spoke with someone last year that layers a lot of maples and they said some varieties root better without hormone. Have you ever heard or seen this case?
Not about maples specifically, but there are a whole bunch of plants that root pretty OK without hormones. And a lot of them perform better without rooting hormones applied.
The most commonly known auxins are IBA and IAA. Both IBA and IAA are produced in plants naturally, but the natural presence of IBA is usually very low (my guess is in a 1:50 ratio IBA:IAA, on average). Plants respond most vigorously to IAA but since IAA is chemically pretty unstable, it's hard to work with. Naphthalene acetic acid (NAA) is pretty effective in most cases as well, especially plants that are less sensitive to the indole-acids.
NAA is readily available as a potassium salt if memory serves me right. This makes it soluble in water. Keep in mind that there's also a sodium salt of it, you shouldn't get that stuff because of the sodium.
Sometimes auxins also don't have a solid effect if there isn't a cytokinin to interplay with. Zeatin is pretty safe to use and made from corn. Although, the same theory as below applies; too much of the stuff can do long lasting things.
Most plants produce enough auxins to jumpstart their own roots and we have to keep in mind that if we apply something externally, it messes with things internally. I have in the past accidentally turned my plants into auxin-depleted mutants by overdosing auxins. Genetically speaking, when a plant senses that there's enough auxins to go around, it turns the "auxin production knob" all the way down. This can go as far as turning the entire switch off indefinitely. When this happens, the applied rooting hormone naturally breaks down over time, but the plant doesn't produce any new auxins because the off-switch was permanent. These accidents happen from time to time.
We have to keep an eye out for these accidents though.. Because in 99% of the cases, it's just a knobtwist, but that 1% is really an issue. These knobtwists can last for decades though.
If plants have been treated in the past with agent orange (containing 2,4-dichlorophenoxyacetic acid, another auxin and highly carcinogenic to humans and animals) then they have a super high chance of flipping the switch to off. Not just for one generation, but for every generation to come in the future. These plants then make use of another auxin variety that is yet unknown to science, but is also makes them unresponsive to NAA, IAA, IBA and 2,4-D.
Cool dwarf varieties might have had such a treatment (and survived), turning them into dwarfs. They can still root through an unknown mechanism, but it takes a loong time and application of hormones would act detrimental to root development because it will influence the 'unknown' pathway. We know it influences the unknown pathway because trials have shown that comparison between rooting hormone application and no-hormone applications showed better results for the ones with no-hormone application.
So in essence, if you're not sure that rooting hormones have a benefit, try not to use them and see how that goes. If nothing good happens, you can start applications. If you do it the other way around, then you might have hit a switch already and there's a chance of not being able to go back (this goes for the entire plant, by the way). If you want to be more sure about the effects of a certain hormone, it's always wise to have a look at in vitro propagation protocols. Laboratory people have been doing this stuff for decades and most of them have experimented with various hormone strengths.
www.scholar.google.com is a good place to start your search for [plant name]+propagation.
Tag words that you could use are "vegetative" (cuttings), "in vitro" (test tubes and such), "in vivo" (in real life), "multiplication", "explants".