Way, way more trad window cleaners than there are WFP window cleaners.
WFP is relatively new and it is taking off now, as its a new way of cleaning to so many, there are so many questions to ask, and there are so many elements to WFP, hoses, poles, pole hoses, backpack/van mount/trolley system/trailer mount, brushes, batteries, water tanks, pumps, fan jets/needle jets, off the shelf or DIY and we haven't even got to techniques, painted frames, UPVC frames, hydrophylic or hydrophopic glass...the list goes on and on!!!
So those are just a few of the reasons you are going to see so many WFP questions on the forum.
And most of those that are WFP are also experienced window cleaners to begin with

Ian