The root cause is a failure to understand that Actions are not all-encompassing.
The rules list 5 activities that you can do On Your Turn:
On your turn, you can move a distance up to your speed and take one action.
Bonus Actions
Various class features, spells, and other abilities let you take an additional action on your turn called a bonus action.
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Other Activity on Your Turn
Your turn can include a variety of flourishes that require neither your action nor your move.
You can communicate however you are able, through brief utterances and gestures, as you take your turn.
You can also interact with one object or feature of the environment for free, during either your move or your action.
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Reactions
Certain special abilities, spells, and situations allow you to take a special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else's.
To reiterate, the 5 activities are:
- Move
- Actions
- Bonus Actions (which are not a type of 'action')
- Other Activities (a class containing all miscellaneous activities) including;
- Brief communication
- Object interaction
- Broadly, anything that "does not require an action"
- Reactions (with a note that they can be used on someone else's turn).
Of these activities only 1 of them is an "Action". This confusion and resulting mistaken assumption that everything you do on your turn is an Action has lead to a lot of fundamental misunderstandings about how 5e works.
A special note for Bonus Action:
Bonus Actions are not Actions. They let you take an Action, usually from a select list. "Let" means you have the option, you are allowed to. It does not mean that Bonus Actions are actions.