4th edition let you 'trade down' actions, so you could trade a Standard for a Move, or a Move into a Minor. I don't know why 5th edition didn't let players do this with Actions/Bonus Actions.
still makes NO SENSE to me that a bonus action can’t be used in place of a regular action… why tf would you not be able to give up your regular action for an additional “particularly swift action” 🙃 5e… what a strange creature