My smartphone benefits over a feature phone:

1: Messaging groups with friends through various apps.

2: GPS guidance while driving.

3: Built in phonebook / addressbook of local businesses.

4: Email access anywhere, useful to access tickets to events or return codes / receipts when needed.

5: High Quality camera always available.

6: Access to NOSTR.

7: Able to pay businesses with a lightning wallet.

8: Able to do personal banking on the go. Quickly check balances, do transfers, and make payments.

9: Access streaming music/videos anywhere.

And more I'm sure that I'm not thinking of. For me, a smartphone is much more useful than a feature phone. But I do think I'll implement the do not disturb mode.