What's the purpose of very small municipalities/communities?

I’m talking those that are around 10 streets.

What are the purpose(s) of such small places? What prevents them from being annexed by larger neighboring cities? How does their economy survive without a lot of stores, restaurants, and gov’t buildings?

Small government that the voter can control vs large gov that come election times your choice is bad or extremly bad. They survive on lower expences. Mayors that are paid less or not at all, volunteer fire departments and such.

Can the annex to larger cities if the want yes, it takes a simple majority vote. Should they probably not. The citizens of Alveso were promised much if they just voted to anjexed to San Jose. And after the annex happened the mayor of San Jose told the new citizens of San Jose that the city could not afford to spend all that money in one district.

Just to clarify, in Missouri it takes a simple majority vote of both the area doing the annexing and the area to be annexed. So if my neighbors and I don’t want to be gobbled up by the big city next door, we can vote it down and it doesn’t matter if 99% of the bigger city votes yes.

As for the rest of your questions, there are a lot of reasons why small municipalities exist. Around here, the legend is that one small town split into two very small towns because the people in one half wanted sidewalks and the people in the other half thought it was a waste of money. There are other small towns that were incorporated because the residents didn’t want multi-family housing, a large shopping mall, an industrial park or other entities that only a municipality could zone against.

As for revenues, Snnipe got it in one. Part-time city employees/officials, limited services, etc.

The ability to annex, like everything else in the U.S., varies greatly from state to state. In some states the majority of both communities have to approve. I believe that in some a vote of the entire county is required. This makes annexation virtually impossible.

As for the OP’s question, turn it around. Why would any other community want to take on a burden? What’s in it for them?

Each state also has different rules on what constitutes a municipality. In New York, you can legally have cities, towns, and villages, with varying requirements and responsibilities. But there are also literally hundreds, if not thousands, of other assessment districts that cover schools, police, water, and other necessities. Very small communities have their police functions covered by the county sheriff’s office and their schooling by a consolidated school district. Fire is either a volunteer fire district or a larger community’s. Taxes are mostly paid, therefore, to larger areas. They exist as outliers to those areas with few local costs. Not much different than an individual farmhouse, really, for which all of the above must also apply.

I don’t know what went into the creation of some of the microcities around Kansas City, some of which are as small as a few blocks, but they are usually filled with high-end homes that give the community enough of a tax base to pay for the services it needs. The microcities may contract with surrounding communities or a county for services such as police protection, water, sewer, sanitation pickup, and so on. Why stay separate, then? Mainly prestige. A Westwood Hills or Mission Woods address is far more prestigious than a Westwood or Fairway address.

Microcities avoid annexation because they’re incorporated cities or villages, depending on the state. A city usually cannot annex another incorporated area.

Many microcities were founded as independent rural villages, but they were eventually surrounded by a larger, faster-growing major city. A few microcities were founded as black enclaves, for example Linndale, Ohio (incorporated as a residential area for railroad porters; today it’s not a black community, but better known as one of the nation’s most notorious speedtraps - another revenue source for a tiny town) and Kinloch, Missouri.

I don’t support the creation or maintenance of microcities for far too many reasons to describe in a simple post, but it’s something many regions have to live with.