Is it because people don't read messages and don't collect receipts?

No, SMS receipt service is a value-added SMS service launched by operators for individual users. After using the mobile phone to send SMS normally, the mobile phone will immediately display the words "Message sent". But this only shows that the short message has reached the short message center normally; Doesn't mean the other party received it. The short message receipt service refers to the service that the system sends a receipt to the user in time after the user sends the short message, prompting whether the short message was sent successfully (sending port 10658007). Specifically, it refers to the service that the system sends a receipt to the user in time after the user sends the short message, prompting whether the short message is sent successfully.