Strava is preferred for creating routes as its the most popular app for tracking rides, and most people in the club use it. As almost everyone has a Strava account it makes route syncing very easy.
Other routing websites or apps can be used, but it's recommended to provide a Strava option as well. The website has a field for the Strava route and also for an alternative. Many club members have Strava subscriptions and can convert other routes by uploading a GPX file to the Strava routing page
There used to be a workaround to create Strava routes withut a subscription, by uploading a GPX as a ride and then converting it but that no longer works.
See this page from DC Rainmaker on syncing routes to Garmin devices
Strava NOTE: Do not use the Strava Connect IQ app, its no longer required