Well, these guys are simply too big to fail. Equifax cannot go bust, otherwise loads of consumer credit (mortgages, car loans etc) would freeze up, causing huge harm to the economy.
The market likely knows this, hence the stable stock price.
Genuine question, how are Equifax's services functionally different from the other credit bureaus? What is to stop the federal gov from shutting them down to protect national security forcing any business partners to move to the other providers.
My company would be really hampered if Equifax went bust. We do use two other credit bureaus, but some functions depend on data only Equifax provides.
We also use the different bureaus together for cross checking, often one bureaus file will be out of date or have errors, while the other is fine. So we'd have a much harder job of calculating risk if one of the big bureaus went out of business, simply because we'd be losing a major data source that drives our business.
I am very sure this case applies to other financial institutions as well.
The market likely knows this, hence the stable stock price.