One criticism that you will sometimes hear about development is that the construction of new housing can spur gentrification. The thinking, I think, is that when you create new market-rate housing, richer people will then move in and the area will begin (or continue) its ascent upwards.

If on the other hand, one were to just stop developing new housing, then the neighborhood would remain stable and static and the fear of gentrification would simply go away. But the flaw in this line of thinking is that it assumes no infill development equals some sort of urban homeostasis.

Cities are constantly changing. The reality is that what we are talking about, particularly in the case of low-rise single-family areas, is that we want the physical character of neighborhoods to remain more or less the same. But what happens on the inside is whatever.

Here's an example:

What you are seeing here are 4 electricity meters, meaning that at some point this structure housed 4 separate homes. But 3 of the 4 meters have now been removed, which presumably means that this structure has been converted (probably back) to a single-family home. So this is 4 homes being reduced to 1.

I don't know what this place looks like on the outside, but I'm going to guess that not much has changed in terms of its physical character. It probably looks about the same. But this is still gentrification; it is still an example of a neighborhood moving upmarket.

The irony is that we tend to be generally okay with this change. We are okay with reducing the number of homes in a neighborhood so long as it happens in a largely inconspicuous and convenient way. But what we are (sometimes) not okay with is increasing the number of homes in a neighborhood. Apparently that creates too much pressure on the existing housing stock.