The built-in note apps are excellent at one thing each: keeping your notes inside one walled garden. The Apple one is great on Apple devices. The Google one is great if your whole life is Chrome and Android. The Microsoft one is great if you live in Windows. The moment you have a Mac at home and a Windows laptop at work, or you switched phones last year and changed ecosystems, the cross-device story collapses.
You can paste notes between apps, but then they're snapshots, not the same note. You can email them to yourself, but then you have to search. You can use a giant note-taking suite, but you wanted a sticky note, not a second brain.
Sticki.ly is the smallest possible answer. One signed-in sticki, the same sticki on every device you own, regardless of which OS made each device. That's free. Pro just removes the cap at sticki #2.