My mobile phone has a message receipt, but I didn't receive it when I sent a message, and there is no receipt whether it was sent successfully or not. Why? I'll send it to someone else

If you are an Apple phone, you only have a receipt for sending a text message to the Apple phone, and the other party has a receipt for reading the text message, while the Android phone has no receipt. If you are an Android phone, either the other phone is turned off, paused, stopped, airplane mode is turned on or your number is blacklisted.