It is the usual way to say that John is going to buy some bread (or whatever else is sold there) from the baker’s shop. Even the cheese bakes are selling bread, and when it is the time to clean it up in the oven it is still very hot. Our dictionary uses the word shop. The phrase is implied or elaborative (by mistake, we know it’s there), but neither do we write it, or say it.
What is the relationship between a baker and his shop? The shop belongs to the baker. When we say he’s been to the baker’s, we’re talking about the bakery and not the cafe.

In the same way we could say:

I’m going to my aunt’s for the weekend.

I’m going to my aunt’s house. Leaving a mark at her house and saying “I’m going to see her someday.” When

you have a s, you have always the same grammatical

construction as ‘. If you say: John’s book.

In the latter “book” has to be expressed because we would not guess what is implied.

This is called the genitative. For more see here.

What is the need of the hour?