When we talk about staying somewhere, we use the preposition "at." (I am staying at the bar).

If we talk about going somewhere, we use the preposition "to." (I am going to school).

Why are we allowed to leave those prepositions out when we talk about home?
I am going home.
I am staying home.

I got asked that question this week and was stumped. Is the answer, "just because?"

indeed, it is 'just because' .... one of the irregularities of the English language, in some countries, 'I am going to home' is actually common

Actually, after a little searching, I found an answer that makes sense and fits even the dictionary.

In that case, home works as an adverb to mean "to home" or "at home."

That sounds right. I've noticed that the words that came into modern English from middle or old English or earlier have these little quirks.

http://grammar.ccc.commnet.edu/grammar/prepositions.htm
This is an extensive discussion about prepositions - what to use, when to use them, when not to use them.

The reason why we can leave out the prepositions "at" and "to" when talking about going or staying at home is due to the unique nature of the word "home" as a noun. In English, "home" functions as both a noun and an adverb.

As a noun, "home" refers to the place where someone lives or where they consider their place of residence. When we use "home" as a noun, it does not require a preposition because it already implies the idea of being at or going to a specific location. For example, saying "I am going home" is equivalent to saying "I am going to my home."

On the other hand, when we use "home" as an adverb, it signifies the direction or destination of our movement. In this case, it acts similarly to a preposition, indicating the direction of our movement without the need for an additional preposition. For instance, saying "I am going home" is the same as saying "I am going to my home."

Therefore, the reason we can omit the prepositions "at" and "to" when talking about going or staying at home is because the word "home" itself encompasses the idea of location (as a noun) or direction (as an adverb). It is a unique linguistic feature specific to the word "home" in English.