Just use a password manager so you can have a different password for each site. It's not that hard.
Additionally, I don't understand why companies continue to roll their own payment processing rather than paying a service that knows how to do it. I guess it seems easy...
There are various "financial hammers" these types of breaches will induce, depending on the network (Visa, MasterCard, etc.). Plus, processors (the banks) will put the liability onto Merchants which are shown to have violated thier ToS. Storing PAN's in clear text (or at all in some cases) is certain to trigger one or both of these ramifications.
Fully outsourced payment solutions are a good fit for some business models but not for others.
One thing I would add is that PCI DSS is also applicable for ISO's as well VAR's which operate payment processing gateways.