Auto incrementing ID as primary key on all tables

I am designing a database for an e-Commerce website which uses MySQL. I have made the list of tables necessary and all the fields necessary for the table. I have a total of 9 tables.

What I have done is include an auto incrementing ID as primary key on all the tables.

All my tables except 2 are normalized to 3NF. Two tables 'users' and 'outlets' are not normalized to 2NF.

Along the way I realized that normalization is cumbersome when using auto incrementing ID as a primary key. As normalization is not strictly required, I want to know if there are any downsides of using auto incrementing ID as primary key on all the tables?