The tactic is attractive because it produces a visible result quickly. Publish forty
pages targeting forty city-plus-service combinations, and for a while some of them rank
for low-competition terms. A monthly report showing forty new ranking keywords looks
like progress, and the agency has done a few hours of work.
The problem arrives later, and it arrives as a step rather than a slope. Sites carrying
large numbers of near-identical pages get caught by spam systems or by manual review,
and the recovery involves removing the pages and waiting — frequently for longer
than the traffic was ever worth.
The uncomfortable part for a business is that by the time it happens, the agency that
built them has usually moved on, and the cost of cleanup lands on whoever is there
next. I have inherited several of these, and the conversation is always the same:
remove them, redirect what has genuine value, and rebuild properly.