Which companies do have name badges? Is that actually common? It seems incredible to me that any would require employees to wear name badges unless they were customer-facing. (Eg. retail)
Microsoft does. Our badges serve as keys to get into the buildings. We can also store money on them for use at the cafeterias.
They aren't really there to tell people your name. Most people wear them on their waist so you can't read them. But they do identify you as someone who belongs, so security can chase you out if you don't have one.
Where I work we deal with healthcare related data and that comes with HIPAA requirements. So all doors allowing access to an area require a photo id/name badge/keycard (except the bathroom). We don't have to wear the badge but you need it to get around. So I just keep mine in my wallet. Also we have cameras monitoring all doors. And patrol dogs with lasers.
They aren't really there to tell people your name. Most people wear them on their waist so you can't read them. But they do identify you as someone who belongs, so security can chase you out if you don't have one.