I've a very modest round compared to the earnings stated by many on here but it affords me a nice house and good lifestyle with hours to suit me. I don't worry about getting work. I'm lucky to get walk ups and enquiries / recommendations all the time without the need for a website or any canvassing or advertising. Do a good job and prove yourself to be reliable and trustworthy and you've no reason to worry about all the others.
However, if I were a new start up I'd need to put considerably more effort in to generating work.. It must be 2 -3 years since I saw any trad cleaners on ladders where I live, yet wfp cleaners are almost a daily occurance, some I know / recognise, but many I'm seeing for the first time. There is a lot more competition out there these days.
There are enough windows for sure but the demographic for those with a disposable income without a window cleaner and needing one is diminishing, well where I live and IMO anyway.