Learning to disable buttons on the example of "Megaphone"

Gentlemen, engaged in web development, I ask you to pay attention to such an elementary thing in your work as a disable buttons. I am constantly confronted with a similar curvature and today is no exception - a “blooper” on the official website of Megafon.



Is it really difficult for developers to insert simple button disable after a user performs an action, especially requiring waiting and inactivity from him, instead of writing messages - “User, please do nothing”.
A simple recipe:
input type="submit" onclick="javascript:this.disabled=true;"