Exactly what badguider said. People need to earn a living wage.
But, it's not just the big companies paying minimum wage. Small employers do it, too.
I know most people employed by cleaning companies make the minimum wage. Maybe slightly more for domestic cleaning, as they will then average minimum over a day of cleaning and travelling to houses.
Self employed independent cleaners tend to charge £10 or so, but that's not too much when you factor in holiday, no pension or sick leave, and the travel time and expense.
I aim for £15 per cleaning hour, but I have a lot of overhead for materials, insurance, travel, accounting, laundry, etc. I think I'm left with £12.50. But, that's for cleaning hour. I may clean 30 hours in a busy week, but there's other, unpaid work I do ranging from going to quote to sorting supplies. And travelling between clients. So, I probably make £10 an hour overall. And still no holidays, sick pay, or pension.
And some people think I'm ridiculous to charge so much.
Many cleaners are off the books, cash in hand. Not paying tax and often getting some benefits.
We all need to look at our own roles in this system.