This is the very question that ALL cleaning businesses should be asking themselves. In the UK, cleaning services of all types are in great demand, be it a person who works alone, an agency, or some sort of business with staff. The actual need to advertise is, for many, unnecessary, as the work generally finds the service provider, through word-of-mouth, from existing clients, and from a local reputation.
Some of the bigger companies do have to advertise occasionally to ensure that the number of their clients on their books matches the number of staff they have available to do the work, and new start-ups have to advertise to get those new customers coming in.
However, I will die on the hill that no person anywhere looked at the before & after pictures on the facebook pages of various cleaning businesses and was more impressed that company A shifted more skid marks than company B. Nor did they look and think "hey, our bog could look like that!" and then suddenly decide to hire a cleaner. It's crass, and it's not the problem people are facing - anyone who needs and ultimately wants a cleaner knows they need one and mentally is ready to hire one. It is finding one that is the problem.
And in that is the "problem" they are able to solve (at least should be able to solve, if it is they are advertising for work), which is that a lot of cleaners and cleaning service providers are -for a great many reasons- unable to provide a regular and reliable service. So rather that showing pictures of homes they've cleaned -which as others have already suggested shows that they've no problem in taking photos of your home, and will have used time that could have been spent cleaning to do so, and the "after" photos in many cases are still of pretty shitty surfaces which only another cleaning professional such as me could ever appreciate the amount of time and effort that went into getting it to look as bad as it still does (and don't get me started on folded toilet paper & towel sculptures) - they should be advertising how reliable they are and what availability they have, as these are the two issues a would-be customer is likely to have faced with previous service providers.
It's not as if there aren't enough "big players" around whose advertising can be emulated - Molly Maid is a huge international brand which has individual franchises in a great many UK locations...all they ever do is tell people where to find them and list a few of the key features of the services they provide. There is no reason why anyone else has to do any more than that.
However, and -in my opinion - sadly, the world has moved to such a point where some people in business have been completely brain-washed into thinking that if they aren't posting endless shit on the internet then they aren't actually doing anything in real life. The whole concept that empty pots make the loudest noise is something which has been lost on some.
As for the carpet cleaner who allegedly showed a soiled carpet from an older persons home, I have, sadly, seen the exact sort of photo years ago, and it was truly heartbreaking, not least because not withstanding the obvious brown soiling on the carpet in front of the toilet pan, it was a very, very clean house that looked like someone had taken a huge pride in, seeing how well presented it was. The decor and equipment in the pictures (walking frames and hand rails etc) had all the hallmarks of it belonging to an older person, and frankly I was ashamed to say I worked in the same industry as the person who had taken & uploaded those pictures.