blockchain database - why so redundant I've become interested in blockchain databases. Everywhere I've read it said that each user has to have his/her own copy of database.

Why can't distributed blockchain database be 'distributed' to reside partly on many computers to achieve say fixed 10 times redundancy, not times number of users redundancy? Will speed be times slower or other reason it's not done?
See https://en.wikipedia.org/wiki/Blockchain_(database)#Decentralization, which states that "Every node in a decentralized system has a copy of the blockchain. This avoids the need to have a centralized database managed by a trusted third party."  

This is as true of 10 computers as it is of one.  It's not about redundancy from this perspective, though that is certainly a motivating factor.  It's about having zero centralized authorities,  and the only way to do that is to allow everyone to have a copy of the blockchain.