There is literal free - actually better than free, you get money for living expenses while enrolled - job training available to them as US Citizens.
No one sobbing about student debt repayment seems to have ever heard of Job Corps
www.jobcorps.gov
Its for filthy vocational training where they will have to work instead of getting a gender studies degree and smoking pot for 4 years while running up six figures of debt.
edit: Sorry to answer the question, its a normal human impulse to feel sympathy towards someone, especially a young child, who has suffered a loss, and contributing to a college fund is a way to express that sympathy, and viewed as a way to not merely cover living expenses but to allow them an opportunity to improve their lives since they will not have two parents to help cover their higher education.
So you are not wrong, there should be no expectation of internet strangers to cover their bills. But that doesn't change that many internet strangers who feel conflicted about Lowtax's passing ("he was a piece of shit, but was a formative figure in this thing I enjoy(ed)") would view an education fund for his daughters as an acceptable outlet for their sympathies.
Even if its largely unncessary now since since universal Federal Financial aid exists and other programs like aforementioned Job Corps.