Several reasons: You might want to run other (possibly non-Ruby) apps on the same server; you might want to tweak settings, like the headers for certain files,

Several reasons: You might want to run other (possibly non-Ruby) apps on the same server; you might want to tweak settings, like the headers for certain files, to improve performance; you might want to do some URL mapping at the web server level; and you might simply want better static file serving performance (nginx is very, very fast). That last point isn't an issue here because Passenger Lite has an "nginx core." So if you can configure that core, then the only reason you wouldn't want to use Passenger Lite in production is if you have non-Ruby apps you want to run on the same server.