I assume it depends on the detail. Minimum frontage set backs require the home to start x feet from the street. Most people don’t want to lose a little space in the “pop front” so the rest of the home is extended back a couple feet. I have no idea how this all pencils out but it does cost something. Same with adding a turret or other ornamental details. If you know which blocks to look for, you can see homes get simpler and simpler until they are square brick blocks with flat roofs (like Riggs Park).

I work in construction for a general contractor, and yes it does cost more and developers in major cities skimp out on this. It’s called ‘value engineering’ — essentially how can we achieve the same goal for cheaper or how do we just get rid of it all together by changing the design. Most of the time it’s by doing the latter. This can happen not only with aesthetic design but also HVAC systems, electrical systems, etc.

The material to add details like this isn’t necessarily the most expensive part, its the labor to do it if you want it done right and not cheaply. We’re at a time where skilled trades are already struggling to find people and to keep/pay people is very hard. Big trends in design/construction are a factor of a lot of things all at once.