The private key is safe from any exfiltration, and usage only requires a short PIN instead of a long passphrase. The TPM ensures you're physically typing that PIN at the machine not a remote desktop window or other redirection that could be hacked.
Obviously, this is problematic/annoying for scripts and things that can't share the SSH session, because you need to PIN with every authentication. Also, for encryption, you want to use something where you can backup the private key before stashing it in the TPM. Windows allows you to do this with certificates that are exported for backup prior to encrypting the private key with an unexportable TPM key in Hello.