Maybe compared to Trump...
But Warren and Sanders constantly promise things they know they won't be able to, and therefore won't have to, deliver; such as free university.
They're idealistic dreamers. The fact that a lot of US voters don't even want those things makes it even stranger they would say those things.
Which is a problem, since promising things that people don't want can lead to accusations of 'throwing money away' or 'tax and spend'.
I do realize that
some people may want things like free college, but its certainly not universal, and right now the majority oppose it (52% oppose, 45% support.)
Frankly, I think Canada has managed to strike the right balance... university/college isn't completely free, but much of the cost is highly subsidized, and significant student loans are provided, so college/university should be obtainable by almost anyone. (We actually have more post-secondary enrollment/graduates per capita than Denmark or Norway, both countries with free post-secondary tuition.)