Such password managers store the necessary information (e.g., website addresses and usernames) in plaintext, which security-conscious users consider an unacceptable vulnerability. If the vault data are leaked or stolen (from either the server or from your local devices), then the attackers will know where all of your accounts are, and what username you use. This opens you up to all sorts of risks, including social engineering or phishing attacks (leveraging the known information to appear credible), targeted brute force attacks (against any high-value accounts found in your vault, such as cryptocurrency wallets), or even blackmail (if there are any embarrassing or unsavory websites stored in your vault).
The 2022 Lastpass breach was a big scandal in large part because their vault database contained website and other account data in an unencrypted (plaintext) form, putting their users at risk, and leading to a loss of a half-billion dollars’ worth of cryptocurrency.
Because Bitwarden prioritizes vault security (sometimes requiring compromises in convenience), all vault data (including website addresses and usernames) remain fully encrypted and unavailable for display until the vault is unlocked. Thus, I don’t see any prospects for implementation of this feature request.