You could argue that features can make it easier across products, but each product would be big enough on their own to develop these features at little cost compared to their income. Apart from that there's no potential upside I can see for a user to have these products under one company.
The same applies to Giphy. Right now, messenger companies don't own Gif companies and it's still very easy to use them together. I don't see the benefit here for a user to have them owned by the same company.