Yes existing homeowners in existing neighborhoods are often quite happy with the product that they purchased (house, neighborhood, local amenities, basket of local public goods attached to it), and don't want it to change very much. But those voters only exist after they've purchased the homes that are built, and the laws and zoning codes/rulings which prevent developers from doing other things are in place before they get there. And all of the various subsidies for certain kinds of development, of course.
I will grant that even in my urban hellhole, demands for parking for new projects do often come from existing residents. While I'm usually not one to play the "dumb voter" card, I do think some, though not all, of these people are acting against their interest because they don't understand the consequences of what they're advocating for. More parking=more cars, not necessarily more available parking.
...and, yes, often people are against infill development no matter where they live, sometimes rationally and sometimes I think not. There's a giant empty parcel near me which will one day be developed. It "should" be a big development, though not any big development, because it's on a main artery and next to a subway stop. Some in the neighborhood will probably oppose anything with too much commercial/retail, with legitimate concerns about delivery trucks and similar. Some in the neighborhood will probably, mistakenly, oppose anything which doesn't include a lot of parking. I probably will neither be happy with what a developer proposes nor with what fixes the local neighborhood tries to attach to it. All of that means there will be a lot of opposition to any proposal, but that doesn't mean that there should be an empty lot there forever.
