Why does packet don't need trailer/footer while frame needs it?

I am trying to understand networking concept regarding OSI & TCP/IP layering. I have googled a bit and it says that the footer in data link layer pdu (frame) is needed as a mark of the end of the pdu.

But why does packet data etc in the layers above it doesn't need footer to mark the end of the pdu as well?

![enter image description here][1]

thanks in advance [1]: https://i.sstatic.net/ndZjU.gif