While I agree with you that shoes are a basic necessities, I bet there are a bunch of families that can afford $60 shoes for their kids but not $600 shoes. This kid is a genetic outlier and that makes this one of those situations where a community can come together to help someone with a unique problem. His community donated $12k before Shaq got involved, so Shaq's charity is just icing on the cake. Also worth noting that Shaq has done work to make shoes more affordable for all people but it's an unreasonable expectation for him to stock every Walmart with Size 26 shoes.
...because its an outlier? I can't even find shoes with half size increments above 11 much less anything above a size 14. 23 is just not something that the majority of shoe companies will produce, much less shoes store stocking them.