It's not like "real" influencers are very real either. When you look at a lot of influencers what you see is just a persona constructed to appease whoever tossed them the biggest bag of money. And that's all great from a sponsor's perspective. It's when they stop being marketing tools and becomes real people again that you may get into trouble.
In today's world you have a mob out there waiting for people to fuck up. And when people do fuck up the mob will make sure to tell the whole world (sometimes in caps) that those people fucked up. And if one of those people is associated with your company or product, that person might cause damage to your brand. A virtual influencer solves the problem in that you no longer have to worry about what your influencers do when they drop their personas and start acting like real people again.