This is silly. You can’t say all liberals march in lockstep on anything, but this is as solid a correlation as any.
Suburbs kill the environment; they are individualistic yet obliterate regional culture at the same time; they are traditionally less ethnically diverse (and created in many cases by “white flight”); they are not friendly to bicycling and walking; they are unsophisticated and crassly commercial in their architecture; they lack most of the cultural amenities found in a core city. What’s not to dislike?