It mostly has to do with planning and zoning along with economics: where can people find work and where do they want to live. Quite often employment is concentrated together: offices and related service industry tend to stay together for efficiency and commands high rent (above typical employees affordable costs per sf), leisure/life style is per sf lower (away from center of commerce) and living clusters closer to that. Commuting time is a combination of two things: total distance and speed (public transportation/ITS highways can increase speed).
Dense cities often have legal restrictions on sprawl (Portland, OR) and/or more inclusive zoning.
Where people work and how people work is not easily managed by designers – they can influence smaller scale projects or create spaces that integrate both work and play. cost of housing and pay is what typically drives commuting necessities though.
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