i was wondering when you hover an element from your twitter profil as 'number of tweets' you have this tooltip comming out.
Why do they need to repeat this information ? Is this for an accessibility purpose ?
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In all honesty even the big companies don't always practice proper UX. There is no reason to ever have a tooltip that says the exact same thing that is already stated. It is a waste of time, resources and overall won't benefit the user in anyway.
Tooltips are used to inform the user of what they are hovering over if it is unclear from what is already stated on the button or notification.