What we need is a database that can both scale-up and scale-out. Most distributed databases offer poor efficiency and performance on a per node basis, which has a high operational cost. This is why people avoid using distributed databases unless they need it. A scale-up database can serve as much workload as pretty large scale-out database in practice. This discontinuity creates the market for scale-up systems.

There is literally nothing preventing distributed databases from having excellent scale-up performance too. Unfortunately, people who design distributed databases have a strong bias toward unnecessarily throwing hardware at performance and scalability problems. This is partly because very few people know how to design a modern scale-up database; making something (trivially) distributed is easier.