It evades me on which page you are. Are you on the customer page - what shows 50 customers at a time? Or are you exporting a complete csv list of customers.
I checked my Customers page and it doesn't use the cart_product table at all - while in you pictures it is the top consumer. So I get the impression that you have some module that adds extra information.
As you seem a fan of not telling too much I will add some of my statistics in a webshop where customers have smaller and less orders so that you can compare. This is an old copy of an existing shop:
Here are my top tables from Tables stress:
And here is my top query - including the information that you see when you scroll to the right:
