The person considered easygoing may simply be the one whose preferences usually win.

It costs nothing to be relaxed about a plan that already suits you. Someone whose preferences are quietly the default never has to negotiate, so they never look difficult, while the person asking for a change carries all the visible friction. Temperament and position get confused constantly, and whoever gets more of their way tends to be credited with a better character. Ease is often a description of circumstances rather than of a personality.

Notice, in a group you belong to, whose choices tend to be the starting point; if they are often yours, propose someone else’s for once and watch how flexible you turn out to be.