In the community where I grew up (and the community where I lived from 2001 to 2010) residential streets all had boulevards. Your front yard would go down to a sidewalk and then between the sidewalk and the street would be a strip of grass with trees planted at intervals between the driveways. This community does not have these. And I miss them.
Boulevards are a blessing. In the winter they make snow shoveling easier (both by allowing one to pile snow on both sides of the sidewalk and by providing a buufer to keep people from driving on the sidewalk and packing the snow down before one can clear it). They make street cleaning more effective because plowed snow can be piled on the boulevard without blocking foot traffic or needing to be hauled away. Year round they make it safer for pedestrian traffic, particularly children, by keeping them farther awayfrom (and less like to stray onto) the street.
But more than that boulevards, in my opinion anyway, have a civilizing effect on a neighbourhood. THere is a far different feeling to walk down a street with grass on both sides of you and trees shading the path than there is to walk down a street where cement and asphalt just run together. In a mature neighbourhood, where the trees have grown tall (and in my experience boulevard trees are generally deciduous so you have the canopy effect rather than evergreens with branches reaching out all the way up the trunk) it almost gives a park sensation in a way. A community which mandates boulevards is making a statement about green space, about priorities.
It is my belief that developers don't like boulevards. They take up space, even that 4 ft width adds up over a few blocks. ANd that means fewer lots can be fit into the same area. Knowing how much prime farmland has been lost to urban sprawl I can have some sympathy for making best use of urban space. Some residents grow resentful over boulevards. They feel that it is unfair to be responsible for the maintenance of the grass on city property.
But on the whole I miss boulevards. They make a city more livable somehow.