Part of the problem here is that we are still in the infrastructure phase of blockchain development, so most dapps still rely on multiple centralized services. But as the infrastructure develops that will shift. For example, (i) all of the blockchains are working on scaling, (ii) Sia, Filecoin and a few others are working on blockchain based storage systems, (iii) Maker Dai, Basecoin and others are working on a stable coin, (iv) 0x and others are working on decentralized exchanges without custodians, (v) many are working on making addressed and key management easier, (vi) distributed identity verification and 'user trust' systems are developing, etc. All of that will take time, but as systems develop, more complex and more truly distributed dapps will be enabled.