I enjoyed my 5 minute walk downtown tonight to pick up my dinner and the 5 minute walk home. Building density so people who want this can live near the services enables people who want more space to live further away and have to drive their cars. I don't know how you build the infrastructure we would need to support everyone driving everywhere as population continues to grow. The cost of it (supported by taxes) is astronomical. 

I find it interesting that all the serious candidates in this forum differ only slightly in their approach to density and transportation. Once you spend time looking at the numbers it's hard to figure out a different approach that actually works.