expand the motivation a bit

EIPS/eip-5920.md

@@ -17,7 +17,10 @@ This EIP introduces a new opcode, `PAY`, taking two stack parameters, `addr` and
 
 ## Motivation
 
-Currently, to send ether to an address requires you to call a function of that address, which has a few issues. First of all, it opens a reentrancy attack vector, as the recipient can call back into the sender. Secondly, it opens a DoS vector, so parent functions must be cognizant of the possibility that the recipient will run out of gas or revert. Finally, the `CALL` opcode is needlessly expensive for simple ether transfers, as it requires the memory and stack to be expanded, the recipient's full data including code and memory to be loaded, and finally needs to execute a call, which might do other unintentional operations. Having a dedicated opcode for ether transfers solves all of these issues, and would be a useful addition to the EVM.
+Currently, to send ether to an address requires you to call into that address, which transfers execution context to that address, which creates several issues:
+- First of all, it opens a reentrancy attack vector, as the recipient can call back into the sender. More generally, the recipient can unilaterally execute arbitrary state changes, limited only by the gas stipend, which is not desirable from the point of view of the sender.
+- Secondly, it opens a DoS vector. Contracts which want to send ether must be cognizant of the possibility that the recipient will run out of gas or revert.
+- Finally, the `CALL` opcode is needlessly expensive for simple ether transfers, as it requires the memory and stack to be expanded, the recipient's full data including code and memory to be loaded, and finally needs to execute a call, which might do other unintentional operations. Having a dedicated opcode for ether transfers solves all of these issues, and would be a useful addition to the EVM.
 
 ## Specification