The play key almost never controls what you meant
macOS decides for itself which app receives your media keys, and it usually picks whichever one made a sound last. In practice that is a video tab, an autoplaying ad, or a meeting app. And when nothing is playing at all, macOS opens Apple Music — even if you never use it.
You know how it goes: you hit pause, your music keeps playing, and something falls silent somewhere else. You hunt down the window, click manually, and next time it starts all over again. A small irritation that repeats dozens of times a day.