Just because you don't see it, doesn't mean it's true. It already has data in it.
Satoshi has inserted text into the txn multiple times, as have many others. It's not unfathomable to have Bitcoin based mortgages or bonds or contracts, all on chain, but you opt for third party networks to process your transactions.
No wonder Satoshi left the project and moved on to other things. There's a lesson on that.