I think you've hit the nail on the head there. Back in Roman times, there were about ~300m people in the known world. That's lots of space to settle into, with a view that you and your descendants will be there for a very long time. They built stuff to _last_, because as far as they were concerned, the Roman Empire was unbeatable, and their dynasties would go on forever.

These days, we're so crammed in where ever there are usable resources, that the moment we die, or move on, someone claims the space and adapts it to their needs. Space is at such a premium that it's illogical to lock it out as one particular usage for centuries.