Finance Bases Questions

1)Payback has more weaknesses than strengths, it seems. So why does it continue to be popular? Can you think if situations in which it might be appropriate to use payback rather than IRR or NPV?

2) It's been suggested that one of the features that makes IRR attractive is that, unlike NPV, it avoids the need to make the always-difficult calculation of the cost of capital. But wait a minute! Don't we need the cost of capital to determine if the project's IRR is high enough to make it acceptable?