I could seriously bike anywhere,

Glad it would work for you. Others who are not so able-bodied or well-located would be prevented from buying groceries, diapers, running errands, or other things they need. Nor could they go visit their friends, go to the park, or other things they'd like to do. Cycling 10 miles in Houston in August is not what most people are going to want to do.

It would be a really big mess, I think

I think you're underestimating how big of a mess your proposal would create. How does a single mom now get diapers or formula if she runs out unexpectedly? How do I get groceries for a family of four? How does someone go check on their parents who live on the other side of Dallas? You're being a bit glib about what impact this would have on other people.