Where are these people when you cease to become convenient?

That is the sad truth in many if not most cases. "Friendships" are often shallow because the friends are. They are often around and inseparable companions as long as they are entertained and there is something they can get from you...but when you need to count on them for anything or you cannot offer anything to or do anything for them, they suddenly are unavailable or disappear altogether. A true friend gives to you as much as they get without "keeping score".

good riddance if they are like that

Burger King?

That is a great way of putting it...
They've gone back to their shallow existence until the want to surface and feel your usable again😭😢

They just vanish because they don't find you interesting anymore. So are seeking something else.

Minecraft

Thank you for best answer.