Coming across this a lot in my graded reader and it’s annoying me… what does てくる add?
why not just say 帰る - to return home?
私が帰ってくるまで
Until I come to return home… could you just say 私が帰るまで until I return home
I think it’s like “Until I have [come to the point that] I have gone home.” I’ve never really thought about it, it’s one of those weird ones that just started coming out naturally after a while…
I would be confused as well
Also some sentences I think is really odd the way they are made like this one
「だんだんと あのやつの事が嫌いになってきていて、今は避けるようにしている。」
the きていて part 
Maybe the easiest way to think about it is to pretend that ‘to home’ 帰る is also a verb in Japanese… Like a homing pigeon or a homing missile haha. Then just pretend the くる ‘come’, adds the ‘come home’ nuance that we have in English.
くる and いく themselves quite often just have a time based nuance. いく means when the verb is being initiated/started, くる means when the verb has come to an end (most of the time). So in this case, 帰る by itself is not actually so specific.
Think of 私が帰るまで as ‘until I head home’ (implies leaving for home), not ‘until I return home’ (implies arriving at home)
In conversation, Japanese are always ‘coming’ and ‘going’ where it seems unnecessary in English.
いってきます！
– literal: I’ll go and come [back]!
– natural: I’m leaving!
ご飯を買ってくるね。
– literal: I’ll buy food and come [back]
– natural: I’m going to buy food
I would also add that it creates a feeling of action that it’s happening soon, instead sometime in the distant future.
私が帰ってくるまで
– you’re probably returning today or tomorrow (you can picture it happening)
私が帰るまで
– you could be returning next year (it’s harder to picture it exactly)
I like these pictures of past and future with time flow:
https://www.wasabi-jpn.com/japanese-grammar/helping-verbs/
ps. There’s several ‘add-on’ structures that add an extra feeling to verbs in Japanese: ～てしまう、～てくれる、～てあげる、～てもあう
In English, you’d just say “my friend went to the airport [to pick me up]”. But in Japanese, it’s better to say 「友達が空港に行ってくれました」to show you appreciate that your friend went to the airport.
That chart (and other variations by other websites) sits fondly in my mind, one of my first “a-ha!!!” moments when learning the language and a lesson I still think about every now and again.
To add on to what others have said, 帰る by itself is only non past and therefore not particularly time specific. Adding the って来る adds immediacy to it. I also imagine that there is so phrasal and semantic drift from 行って来る and 持って来る.
edit: Semantic not somatic lol.