The USB-C ports on your M2 MacBook Air are multi-purpose ports that know how to speak several protocols.
- Charging (USB-C Power Delivery to the MacBook Air)
- DisplayPort
- Thunderbolt 3 (up to 40Gb/s)
- USB4 (up to 40Gb/s)
- USB 3.1 Gen 2 (up to 10Gb/s)
Most accessories are interested in a USB signal or in a DisplayPort signal. USB4 is so new that there are few devices which understand USB4 20 Gbps and USB4 40 Gbps transfer modes yet. Thunderbolt is more capable than USB 3.1 Gen 2, but its controllers tend to cost more to implement. If vendors can do something either using USB or using Thunderbolt, they will normally do it the cheaper way.
So you find Thunderbolt reserved for things like
- 5K and 6K monitors
- Thunderbolt hubs and docks
- High-end external SSDs
- High-end multi-drive enclosures