You must prefer a candidate who says what she would hypothetically do (but of course won't) rather than a candidate who might not be able to do everything she says she wants to do but will do some of what she wants to do. In other words you prefer to help the working class by supporting hypothetical candidates rather than taking a risk with an actual candidate. 
Jill Stein has never served in any official political position in the United States but I guess hypothetically speaking, it could be an asset.