Hey Wael! Thanks for sending along that feedback :)
Technically speaking, this is easier to do in a same-network message delivery. So for example, on iMessage, that's possible since it's not an "sms", it's a VoIP message that is delivered between two numbers on the same network. Since that network can read between the two numbers, it's easy to indicate when something has been delivered.
On a regular voice-network sms, there isn't as much 'conversation' being had between the two opposing carriers to be able to implement this. However, this is something that is being worked on with RCA messaging, and certainly something we are looking into :)