You are making the other half of the argument: Neither actuarially sound, nor a legally binding commitment. I thought the second part was too obvious to mention. But, Hell, it kept the Democrats in Power for four generations, so it’s served its purpose.
It has S.S. has been used as a vote buying slush fund, under the propaganda as an “earned right”, “trust fund”, et al. During election time it becomes a propaganda tool for the politicians in “G-d’s Waiting Room”, aka Florida, and many of the residents are as ignorant about this as the low info voters who blindly follow the demorats.