Common movements can be an advantage
When the movement is a widely available quartz or mechanical caliber, repair or replacement can be straightforward.
Exterior parts may be the harder problem
Cases, proprietary crystals, crowns and bracelets can be more difficult to source than the movement itself.
Traditional watches and smartwatches are different
Connected Fossil devices are electronic consumer products rather than conventional watch movements and are not a core service category.
Mail-in makes sense for more involved work
Simple battery jobs are often cheaper locally, while movement, crystal or crown work can justify shipping.