I think the feet do add a little something to the bowl, the word character comes to mind. Is it worth it? I would think so but maybe not for ALL pieces like these as it is quite time consuming to do those. Once you get the art figured out and efficient at making them then maybe it will be more cost effective to do it regularly.
At the end of the day if you are selling your work it has to appeal to the customer and not everyone wants the same thing. Find something like this that makes your work stand out compared to other people's work. These bowls look great and of the 2 I like the one with the feet more.