Keep in mind the link is page dated Dec 2004. Why use an air tool, well choice would depend on what infrastructure already exists or if there are hazards to using hydraulic or electric powered devices. For example, orchards tend to use air pruners and for those who can afford it, bespoke platforms designed for pruning come with a suitable compressor to run the tools [1] Battery powered portable equipment has come a long way but I still don't see to many robust enough to not have to worry about their use in inclement weather.

[1] https://www.treefruit.com.au/orchard/orchard-equipment/machi...