Why do some stores attach bells to the door?

[Jomar Bro]

Or at some places they have the door "ding" when you step in.

 

[jack]

So they know that someone is coming in.

 

[Ashley]

So they know when a customer comes in

 

[Fan?tico de virus]

i think the shop keepers like a bit of music to their ears..hahaha

 

[Ryann Newman]

to notify the clerks to get to the counter.