The Strava smartphone app could connect directly to power meters and cadence sensors, similar to HR monitors which are already working well.
Not everyone wants to/has the ability to record this kind of data through a dedicated cycling computer ("head unit").
Strava has already had tentative plans for this for years. From https://support.strava.com/hc/en-us/articles/360049550432-Pairing-Sensors-with-the-Strava-app :
Can I pair power or cadence meters?
Our plan is to first roll out heart rate monitors with BLE pairing to ensure it’s working as intended before we expand to power/cadence meters or other sensors. We don’t have a hard timeline but if our rollout of BLE pairing works as planned, you can expect power/cadence meter support to be recording devices that we would look at to support in the future.