That isn't how the game is designed.
Note, I'm not saying you can't play that way, I just think it's bad advice.
Everyone wants to be the one to act first. Initiative helps to be cinematic and have dramatic and tension filled scenes. In my fantasy/action movies I like to imagine that both sides of a conflict want the upper hand. That tension is great, knowing the outcome ahead of time deflates that.
It's not fun to be attacked and not be able to do anything about it. Acting outside of combat is essentially super surprise (as the enemy doesn't even get a chance to use a reaction). PCs and other creatures just shouldn't be surprised if they are aware of their enemies.
I don't think I would want to play at a table where the first person to shout gets to do the thing.
To put it another way -
Greedo declared his action first but Han won initiative.