You're thinking in wrong categories. Suppose you want to buy a table. You could say "I'm looking for a €400 100x200cm table, black" and these are your search criteria. But that's not what you
actually want. What you
actually want is a table that fits your use case and looks nice and doesn't cost much, and "€400 100x200cm table, black" is a discrete approximation of your initial fuzzy search. A chatbot could talk to you about what you want, and suggest a relevant product.
Imagine going to a shop and browsing all the aisles vs talking to the store employee. Chatbot is like the latter, but for a webshop.
Not to mention that most webshops have their categories completely disorganized, making "search by constraints" impossible.