We track our DS's phone and hope that it is with him. For context, he is 14 and has a long journey to and from school which involves cycling across town to catch a train into our county town and then cycling across the city centre to reach his school. It is a specialist technical college that he chose to join in year 10.
We track his phone for multiple reasons.
Cycling through the busy city centre traffic is quite dangerous so it's reassuring to be notified when he has arrived safely at school in the mornings.
He's also autistic and sometimes makes odd detours to bike shops, forgetting to let us know what time to expect him, so we track him on the return journey so we can see which train he caught and know when to put the kettle on/start making dinner 🙂
His social communication style and relationship difficulties have also lead to him being bullied on the street in our hometown so it's helpful to be able to locate him in a hurry if he's being threatened.
If he's cycling out in the evening to meet his Dad, it's reassuring to know that he has arrived safely.
All in all, we find tracking his phone useful on a daily basis.