Many members do not see the viability of winning elections on a separate party ticket right now, we don't control the ticket endorsed candidates use however not using the democratic ticket is not a good idea in most offices and so someone running on a different ticket is unlikely to win an endorsement. There's heavy internal debate over how much resources to devote to campaigns, when/how/if to stop using the democratic ticket. US elections and parties work differently compared to say Britain which changes what is viable. So if there's no push to run on separate ticket, then why run as an official party. There's also historical issues in that DSA was not founded as a party, so to become one it would take an amendment at the national convention, and I don't think such an amendment would pass.