Alcoves inside the barn doorway

I was in two barns this week and both have this alcove really convenient to the doorway. Both on the left side of the barn foundation. Both are timber frame barns, both in WV, USA. One is c. 1880 the other c. 1950. There is no window on the outside, none was stoned over.

I can speculate that this was installed as a convenient place to put things down when entering or exiting, but that lacks the allure of this specialized and consistent aspect of the masonry.

Anyone have a real answer as to why they would go to the trouble to build this alcove when a plank of wood would shelf just as well?

Are they aligned with each other?

Could they be used to secure a temporary barrier for large livestock, like a horse? Just slot the bar in.

How wide are the doorways? Were they perhaps intended at one point for a wagon to park there or horses to pass through? My concern with having a shelf at the entrance of a horse barn is that an animal could graze it as they pass through. An alcove would achieve the same purpose without that risk.

Alternative theory, if it is a more narrow doorway, is that it could have been simpler to construct a narrow passageway (less span overhead). Using an alcove instead of a shelf means the builders wouldn't have had to make it as wide.