Shopping online is easier if you know exactly what you are buying. But when you are browsing (shoes, glasses, clothes etc), the ideal experience is the ability to filter by a hierarchy of attributes specific to that category. This requires tedious data collection and categorization.

Eg. Shoes - there are different kinds of attributes - high level shape, specific stylistic shapes, material, usage, price, brand. This categorization needs to be done cleanly. It can get messy fast. If I start seeing sandals when i searched for leather boots, I will get confused and refuse to trust the results.

My theory is that this is why online retailers focussing on certain verticals are able to get some level success vs amazon (Eg. Zappos), largely due to the level of detail available for the browsing experience, even if their prices are higher. Amazon's UX/UI is too generic and sometimes frustrating.