This law / concept has been around for x number of years without being directly overruled or contradicted. That weighs in favor of not overturning said law unless major shifts in public opinion or unforeseen negative consequences have arisen that are attributable to said law.
In the perfect world of legal theory, it helps build consistency (and thus legitimacy) regarding how laws are made, enforced, and interpreted. No “gotcha” judgments.
It’s efficacy can be argued, for or against, by folks here who are much smarter than me, but it has been used as a shield against changing controversial laws. Conservatives clung to it pretty hard throughout the “rights revolution” of the last 80 years, but really had a hard on for it during the civil rights movement.
Now that the major decisions which created the rights revolution have existed long enough to warrant such consideration under stare decisis, conservatives have easily dispensed with it. Because hypocrisy.