Expressions of support for Sanders are made as a marker of political orientation. Expressing support for Sanders says 'I'm not a moderate, I'm well to the left of most people', and as with most such things, serves to identify a 'cool' group separate from the general run of 'squares'. People doing this do not even particularly want to prevail, in the sense of being in the majority. It is axiomatic that a majority can never be 'cool', the feeling of being 'hip' and part of an 'in-crowd' depends on being outnumbered by the host of the unwashed and unenlightened. The point is not to achieve any political goal, to secure any discrete reform, it is simply to be sure one is perceived as a particular, and special, kind of person.
People who have an actual interest in achieving the goals widespread among Democrats, the goals of all left and progressive and liberal persons in general, recognize readily Sanders is far too flawed as a politician, and as a personality, to make any progress towards their goals. They know Sanders has not achieved any measurable advance towards them in his long Congressional career. They know Sanders' claim to hold patents and copyrights on these goals is nonesense, because they know their own desires pre-date Sanders, and exist in their hearts and minds without the slightest reference to him or influence by him.
In short, while Sanders imagines himself to be the indispensable man, an overwhelming majority of Democratic voters are clear in their minds that Sanders is quite dispensable, and are determined to see him disposed of, as soon as possible.
"From Bernies perspective, dropping out of a race once you have no chance of winning is peculiar behavior that can only be explained by the work of a hidden hand. For most politicians, though, it is actually standard operating procedure. Only Sanders seems to think the normal thing to do once voters have made clear they dont want to nominate you is to continue campaigning anyway."
"When things are not called by their right names, what is said cannot make sense. When what is said does not make sense, what is planned cannot succeed. When plans do not succeed, people become uneasy. When people are uneasy, punishments do not fit crimes. When punishments do not fit crimes, people cannot know where to put hand or foot."