In a short blogpost Michael Dyrynda gives some good advice on why you should cache your routes and config values.

As part of the recommended production deploy process it is important to run the caching commands that Laravel affords us via Artisan. This means running config:cache and route:cache, which will compile the config and route files down into a single file each. In doing so, Laravel aims to speed up parsing of these files by only needing to read a single, rather than multiple files.