I am in the extremely fortunate position to be able to work in a school. Mine and dh's income is very modest, we live in a modest house, we don't have many family holidays (and certainly not abroad).
BUT, the dc know I am home for them after school. I can therefore take them to swimming / hockey training / friend's houses / emergency shopping trip for new school trousers etc etc. I can be there for them.
If I had to work all day I would seek out a child minder or approach a friend / family member.
I would NOT NOT NOT leave them in the same building where they have already spent 8 hours that day.
I appreciate it is a great solution for busy mums (who perhaps don't have the time / energy / inclination to seek something better for their children) but to my mind it is a lazy solution which does not have the interests of the child at the forefront.