Because the onus is on
you to show the substantive difference. Learning from copyrighted works has
always been accepted as free and unrestricted, up until 2022. Before that, nobody (to a rounding error) thought that simply being influenced by a previous copyright work meant you owed a license fee. If anything, people would have been
livid about restrictions on their right to learn.
Only when big-corp critics needed another pretense to support a conclusion they long agreed with for other reasons, did they decide that the right to learn from your exposure to a copyright work was infringement.
If you're interested in the similarities and genuinely curious, you could look at the article linked above, which shows how both LLMs and humans store a high-level understanding of their training set. It's a way deeper parallel than "it's all learning" -- but you have to be willing to engage with the other side rather than just strawman it.