I think the lack of using WFP system in the USA are because;
1. Fewer regulations governing equipment useage.
2. Almost 100% of the time the insides are cleaned at the same time the outsides are. I suppose you could use wfp for the out and traditiional for the in; that is a lot to haul around though.
3. Frequency of cleanings; 2 times per year; maybe 3 tops. Lots of detailing; hands on items. Stain removal.
I charge about $10.00 per window in and out. Sometimes more. If I charged $5 it would still have to be perfect; so I would rather charge for our time.
Remember; we remove screens, clean the windows and the screens, and replace them.
Each time is a "one off" cleaning. Increasing volume is the market here. Charge more; do each job less often but do more jobs.
4. Each house has anywhere from 30-50 windows per; with screens. 85% of the homes over here have window screens.
I do not have screens on my house. I took them off. I see no reason for screens; they are a pain to clean, collect dirt, and for someone that uses the air conditioning or heat only; they serve no purpose.
If a household opens the windows often the screen keeps bugs out. I believe that is the big reason for screens. Perhaps a false sense of security; but if someone wants in a screen is easily removed.
The screens are an issue. Usually in order to guarantee careful and appropriate screen removal you need to go inside to do it.
Lift up the window; hold on to tabs on bottom of screen; lift up slightly and push out; the screen comes out.
Then you have to clean the window tracts really well.
I vacuum out the tracts and also wet clean them.
5. Almost all houses are 2 levels or one. Almost never three. So altho up 2 levels is dangerous; I think the house designs are different here versus there.
Residential is a great moneymaker over here.
I'm sure there are more reasons concerning the differences but the preceeding are the ones I can think of.
I will use WPF one day. It looks great as a choice.
Safe; quicker once you get the hang of it; I would like to learn more.
There will always be traditional methods. Detailing is the plus there.
Both are equally good.
Hugs,
Texas Girl