higher education -- a period in which someone (you, the university and/or the state) spends a lot of money to enable your education -- is a huge luxury. It's a totally fair question to ask "what are you going to do with your philosophy degree?". If you're deeply passionate about your subject, then I think you can justify pursuing education purely for its own sake. But that simply does not apply to the vast majority of people studying philosophy/history/sociology etc.
I could already write and think before university and I had all the mathematical tools that most people ever use in real life. University taught me how to write an academic essay of adequate quality, but I don't think this is an essential life skill.
I think the effect is overstated by selection and attrition. if you're not capable of thinking logically in the first place you probably will not choose to study philosophy or fail out if you do.
once you are a fully developed adult, intelligence is normally very stable. an analogy with weight simply doesn't work: anybody can increase their weight simply by eating more, but we don't know of any reliable methods of massively increasing or reducing intellignece.
yes, there is a huge difference in humanity between someone in who simply misleads about company finances and someone who actively ignores their duty to care for their own children