Shopping Paradox

When I go shopping and head towards the detergent section, I find there are many brands there but when I look closely at the products I find that there are just a few companies making all those different brands. The different brands look like they are competing against eachother but they aren't. 

I don't want to name any shops or manufacturers directly but I will say it is like that everywhere. When I look at the shelves I see many brands but there is just a few companies. This has a fishing net effect because the whole space is taken up by the products of just a few companies.  There may be 6 different brands of detergent on a shelf but they are all made by the same company so if you buy detergent A or detergent B, you are giving your money to the same company.