>> robot that could just lay some bricks

How often does that actually come up in modern construction? We don't really do brick buildings anymore. Bricks are generally only a façade, a decoration, rather than the structure of a building. They have to look great because that is now their job. They have to fit between other decorative features and adapt to curves and non-perfect angles. Previous edge cases are now a daily norm.

I say that the robot brick machine is already common. Those trucks that pump concrete into forms are the automated brick layers. This is an important point for all robotics. It is always very hard to build a robot that can directly replace a human. The way forward is to build a robot that gets the job done using different means. The human "dishwasher" was replaced by a machine that does the same basic task but via very different means. The concrete pumping robot now creates solid walls faster than any team could ever lay bricks.

I do not know where you live, but I can speak for Czech republic (mid Europe): basically all houses are made by layling bricks. Its not "the" small brick, it typically range 10-50 cm in depth, which is its shortest dimension. Sure, theres ytong and such, but that too is essentially a big brick. Module or wood houses are absolute minority here.

In north american, hand-laid bricks are just to expensive. It is far cheaper to build wooden forms and fill them with concrete. Bricks are then stacked as non-structural decoration on the outside of the concrete or wood walls.

My guess would be that the main reason is that in the event of the earthquake you would survive in the second and die in the first.