There are still plenty of reasons why one might want to buy the classic (or flex) fare. The most important one is probably flexibility: A Classic fare can be changed for a fee, while a Light fare can not*.

Remember that every economy seat in the plane can be bought as a Light fare. Meaning that if you book late it may not be a cheap fare at all, in fact, it may be close to the price of a business class fare. In which case spending a little extra to book Classic is, imho, a smart thing to do: You can then change your flight if you need to. When booking Light that (expensive) flight/ticket may be lost when your plans change.

* Depending on POS