Both of those statements are false. Appraisers don't get sued because market conditions may impact the value of a home they once appraised.
Banks/CU's get appraisals for two reasons: 1-they are required to (in nearly all cases) because the GSE they are selling them to requires it....2-because collateral is the ONLY thing in a transaction worth a damn.
Yes, most banks still get appraisals because they are required but there are numerous and growing exceptions. Fannie Mae hasn't required appraisals under the de minimus ($250,000) I believe it was and they've been trying to raise that level to $400,000. Of course we see the requirements decline significantly just as we hit a peak in the market.
Collateral is not the only thing of value in the transactions. The borrower has always been as much or a bigger piece of the value. It's not like they are going to just let the borrower off the hook if the home declines in value.
And yes, many appraisers faced lawsuits after the 2008 decline. There were some that were awful and some outright fraud but most were minor errors. Nobody paid any attention or cared until the market declined.