To create an open protocol which helps coordinate resources towards a common goal, the resources need to be known at some level in the same way a lot of of data on the web needs to be public for it to be traversable and useful. For example: creating a decentralized Uber requires a relatively open dataset of riders and drivers available to coordinate the network.
The problem with this argument is its premise: that there are clear incentives for a decentralized Uber to exist. Decentralized applications are by their nature costlier (due chiefly to the having to break down and distribute your resources unevenly, costs of communication and coordination, etc.), and those costs must be represented in the service provided to the user. All else being equal, the rational user will choose the cheaper service. The only thing a decentralized Uber can have that a centralized Uber cannot is censorship resistance (ie. the inability to report users to the government or block them from the platform and the inability to see who is using the platform). Thus, a decentralized Uber can only operate in a jurisdiction that barely has any laws around ridesharing, for example.
In jurisdictions where the decentralized Uber is allowed to operate, it will be more expensive to use than the centralized Uber because of economies of scale.
These premises imply that the only people that will use a decentralized Uber are those that do not want to be censored or want maximum privacy. As we have seen with things like Tor, GPG, Torrents, etc., it tends to be a fringe group of activists, oppressed groups, criminals, etc.
Once we have agreed that the only incentive to decentralize is to obtain censorship resistance and privacy and that decentralization is by its very nature less efficient, it becomes hard to believe that Google, Facebook and Amazon will simply give up their data and put it all on the blockchain, thus having to provide a slower and more expensive service to their users. On the flip side, it is also hard to believe that competitors to these companies that operate on a decentralized network will ever be able to compete with the centralized services — except when it comes to privacy.