Yes, there is a pure technical reason.

In client-side validation there is no P2P network like in blockchain; you validate only part of the global history and state directly related and interested to you. Thus, if somebody in that history uses something which was valid for him, and you have a newer software in which this have become invalid (like in soft-fork in bitcoin blockchain), you will decline these data, meaning that that part of the history will be lost forever after such a change.

Also, in bitcoin blockchain you can target update events using blockchain as a Time Machine; in client-side validation there is no full order of events and you can't say that "After time point X a thing becomes valid/invalid", so no means of coordinating updates.