Compress then encrypt opens up one important vulnerability: if an attacker can control a part of what you're encrypting (which they perhaps can on an average laptop drive, think a cookie in a webbrowser), and they can observe the size of the message after it has been compressed and encrypted, then with repeated attempts they can guess part of your secret and wait until the compression algorithm succeeds in matching part of their data with your secret.

TBH, with whole-disk encryption I would not worry too much about this attack (the threat model is almost always theft where repeated observations of the cryptext after being modified by someone with the key are not practical), but it was core to a lot of vulnerabilities that basically forced TLS-level compression to be almost universally disabled.