Dumb question. If it's chocolate cake with red food dye, then does it just taste like chocolate cake? In which case, apart from adjusting the colour, why not just make chocolate cake?

Does it taste much different if you use beets?
The beets add more texture than taste IYKWIM? They can and do add a lovley texture and moistness to chocolate cake. They don't however make it takes like a vegetable or anything like that. Hehe, Red velvet cake is mostly about the look of the cake and the contrast with the Icing which is why you will most often see it with cream cheese or butter cream icing.