Why would you think that? It's much more urgent to replace commonly eaten foods like beef, chicken and fish than foods that for most people are little more than a curiosity.
With that said, vegan caviar has existed for years make of algae, and it's honestly not far from the real thing.
I mean, 'Whale' meat or 'Caviar' or 'Foie Gras' instead of ordinary 'Salmon' would find far more market.