I noticed a wedding cake display at my local Walmart.
I used to eat Walmart and other grocery store cake all the time; never really had a custom cake that I can really think of (mainly as I never knew the difference). I've only been to one wedding since really getting into the cake stuff.
Anyway, while it might not be everyone's first option, I think it's good to have another option.
With weddings, some want top-notch everything, some want lowest budget possible, or some have certain priorities. Growing up, I always saw that limos were a given in every wedding; after moving, the two weddings I had gone to, no limos.
I still have the mindset that a limo seems the tradition (just from where I grew up), but I know that if I get married, a limo is not on my priority list. I'd rather put that money into something else that is more important to me. And some people might feel that way about cake; Cake might not be on their priority list, so finding a cheaper priced cake might be ideal for them (taste aside).
Some people might not understand the difference in taste or quality of Walmart cake vs custom, but some people might not care as long as there is cake.
I personally won't buy a (wedding) cake there - If I'm going to have cake, I'm going to make my own or get something custom as I appreciate these things more now that I've gotten into this, but if I get married, I'd probably ask my coworker to do it as she's really good, and I know I'd be able to get a nice cake for a good price.
Anyway, just a thought. A Walmart (wedding) cake isn't for everyone, but it's just another option.