Why is 'to' not used before 'home'?

Solution 1:

In this phrase "Go home", home is not a noun but an adverb

Specifically, it is an adverb of place

So you do not need a preposition like "to" prior to home.

The Longman Dictionary specifies

Do not use a preposition (a word such as 'at' or 'to') before home when it is an adverb

Other similar adverbs of place are listed below, and you can see you can use the same rule to all of them

abroad
anywhere
downstairs
here
home
in
nowhere
out
outside
somewhere
there
underground
upstairs

Solution 2:

I've never been happy with the suggestion of adverbial status of nouns that can just as easily be parsed as objects.

i.e. If "home" is where "I am going", then "home" is the object of the verb. For it to be an adverb, it would have to modify "going", which it doesn't (with "I am going quickly", "quickly" clearly modifies how the "going" is carried out).

The difference between nouns where we use "to" and where we don't is more to do with the non-specific meaning of the object noun.

"Home" is a non-specific place, in this context, in that you cannot put a determiner in front of it without losing its (intrinsic/abstract/personal) meaning:

i.e. none of these work: -- "I am going the home." -- "I am going that home." -- "I am going a home".

For specific places (you can tell they are specific, because you need a determiner to specify which one), the "to" is required.

I don't want to shout down Longmans, because they do an extremely difficult job very well, but sometimes they do drift a little from reality.