Same reason why we don’t publish our public keys to the block chain, and when we do, we abandon them. It’s a complicated topic I can’t fit into 184 chars 😂
But my BCH pubkey for memo.cash is already public and available in these tx. Another rule of crypto: signing/with key is never used encipherment. Ever.
Here's a quick python script to convert that pub key to something you might recognize: https://imgur.com/a/kTr3qkS. So we publish our pub key to the block chain on every tx.
When you expose the pub key, it's a privacy issue. But more importantly, if there's a weakness discovered where the priv key can be found with the pub key, your funds are protected.
A few msgs coming. When you spend money, you have to publish the pub key in the scriptSig of the tx. That's why we have change addresses for EVERY tx: because you expose the pub key.
It compromises your funds, your account, and every message you’ve ever sent. I was about to publish a spec on this and missed a crucial issue, so I’m re-thinking the design.