I think you're actually proving my point.

> We were almost exclusively agrarian before industrialization.

Who's the 'we'? Western Germanic society perhaps, but even there there is no shortage of examples of large urban populations, including for the very rich, who usually preferred the safety of the cities.

> Suburban neighborhoods don't think of people in terms of their front yard. They don't think of front yards much at all, except when it comes time to cut them.

> People like to have space between them and their neighbors. It is a buffer between you and the road, and a place for your children to play. People like to have a space that's theirs.

> The objective function of a suburban area is not to maximize space efficiency.

Potlatch would probably have been a better term, but your points are exactly what I was saying - maintaining a well-manicured lawn is incredibly expensive, particularly in areas where grass doesn't naturally grow well (like desert areas).

> Again, this could only come from a city perspective. Front yards are easy to get. Everyone who wants one has one.

Before you dismiss my point as 'only a city perspective', think about the total expense associated with lawn care - assuming that you don't let it completely go to seed, because this is the potlatch that I was talking about.

Read Alice Walker's 'Everyday Use' and you'll see what I mean - she doesn't describe the lawn itself in too much detail (it's an artifact of the time in which it takes place), but even from the first paragraph it's clear she's not talking about a lawn filled with grass. In fact, she's referring to a "lawn" of dry dirt, which she makes 'wavy' by raking wave patterns into it. There's no function to raking dry dirt any more than there's a function for cutting down healthy grass to 1-2 inches from 5-6 inches.

It's not like there's anything natural about a well-manicured lawn; in most suburban enclaves, it's rare to see more than one row of flowers and other flora - 10% of the space at the very most. If the 'function' of a lawn is to provide privacy, or a buffer, it would be just as well served by an empty lot. Or even better, by tall bushes and trees, which can look just as aesthetically pleasing. Don't confuse incredibly artificial front lawns with 'nature'.

> Why, for instance, do New Yorkers buy their second homes in the surrounding rural areas? Why not another apartment?

Second homes and front lawns have nothing to do with each other. You seem to dichotodmize 'suburban homes with lawns' and 'multi-family apartments', but there's actually quite a lot in between. It's just rare within this country because societal forces have caused us to tend to prefer the poles of that spectrum, for the time being.

> Are you suggesting all the front yards you see are equivalent to gold chains, and not some fundamental property of how people want to live?

At one point in Puritan society, housewives were judged by the number of lumps in their sugar bowl, because that showed how much time the household invested in house care. Today we use other metrics, lawn care being one. There's no fundamental property of how people want to live, except that all societies create largely-arbitrary metrics of judgement (like potlatch) - this just happens to be one of ours today. Don't think that any of these arrangements of living are permanent and universal, as if they spring from some intrinsic understanding of human beings. Look at old Chinese living arrangements and you'll see what I mean, even if you only compare them to Chinese homes today.

> Jackson is an argument on actual suburbanization, not "intra-city" suburbanization. So if you aren't talking about these concepts in general, why predicate your comment on Jackson's book/phenomenon?

Since 1970, only two cities in the country have grown in population without annexing territory from surrounding areas. If you read Jackson's works, you'll see that these two aren't as clear-cut and fundamentally different as you seem to think.