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 button disable. I constantly encounter such curvature and today is no exception to this - a “blunder” on the official website of Megafon.



Is it really difficult for developers to insert a simple button disable after the 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"