Include product page in the silo (URL structure) or not?

We all know the perfect way of categorizing the website into silo's. Now I notice a HUGE websites whom make the websites into silo's until the product page.

As an example:

The domain.com is about pets,
the category page is about dogs so its domain.com/dogs
the sub-category is about dry food for so its domain.com/dogs/dry-food

So far it looks perfect

the product page becomes domain.com/product-name

WHY? This looks so bad..

What are the pro's and con's for directly linking to product pages after the domain?

As I'm talking about the biggest petshop in The Netherlands who doesn't silo the product-pages, I wonder why they chose this structure.

Any expert who can help me understand this?

No one?

Is it just something they are doing wrong? That's also a possibility of course