Silos and grain bins vary in their width. I have seen some seriously wide diameter bins, like 30-40' across.
Technically, the homes shown in the links are based on grain bins, not silos. They often go under the name of "Butler bins" based on one of the larger manufacturers of such bins.
Silos are often/usually used for storing silage (from whence comes the name - silage from silos), although some of the older ones have been used for temporary grain storage as well.
If you notice, most old fashioned silos are either standing empty, in ruins or have been torn down on a lot of farms. They have been replaced with metal bins for grain storage and plastic tarps/sleeves for silage production. They are much cheaper than the big Harvestor silage silos that were popular over the past 30 years or so.