I don't think C/B and H/D hang out with each other either!!
I think the competition between the top 3 American ice dance teams is so intense right now that it’s too difficult to maintain a genuine friendship with each other at the same time. I’m sure they all respect each other but being close when you have to fight each other for the title of US #1 all year wouldn’t be easy. I don’t think C/B and H/D spend time with each other either.
Maia and Alex seem to be good friends with the junior and new senior US ice dancers. They’ve had pictures with the Parsons and Carreira/Ponomorenko on their Instagram recently.
I was at GPF in Marselle and C/B and H/D were not precisely pal-ing around. I know that Madison Chock is very close friend with Ashley and Marissa, and Madison H. with Gabriella P. , I guess the ambient in US ice dance is a little tense, just like V/M and D/W used to be friends and all changed when they were fighting for the gold medal. I guess C/B see them like the team that took their place as number 1 in the USA, and H/D see them as the team that is preventing them from reaching the first place. We do not know if it is Maia and Alex who are moving away from them, or if it is C/B and H/D who are moving away from Maia and Alex, they used to be friends
https://www.instagram.com/p/U8uJmFBdu0/?taken-by=splashmadison, Alex and Evan were roomates.
Anyway, Maia is Alex's best friend, he always says it, and he also always asks Maia if he is her best friend

, to which she always answers yes. So, actually they are super best friends with American ice dancers (Maia and Alex)

. ¨chapis logic¨.
Regarding Hubbell/Donohue: I think slider was referring to this picture:
https://www.instagram.com/p/BcpWjIEF6np/
Keep in mind that Madison Hubbell used to be training mates with Evan Bates way back in the day when Hubbell skated with her brother Keiffer and Evan skated with Emily Samuelson. Madison Chock used to be training makes with Zach Donohue when he skated with Piper Gilles and they were all training with Marina/Igor in Canton. So they go back a bit, hence the reference to "lifelong friends."
It seems Chock and Bates got to know Papadakis/Cizeron better this season -- they were both at Cup of China and Internationaux de France.
I think the Shibs' deep friendships have just come through differing circumstances and they prioritize certain relationships over others, especially given their busy schedule -- let's keep in mind they're doing a lot of other stuff the other ID teams are not, such as endorsements, Pyeongchang mentorship with that Korean middle school, LA 2028 athlete committee stuff, YouTube/social media stuff.
They have been long-time friends with Ross Miner ( I used to ship Ross and Maia at one time

). And it seems their relationships have been forged on Japan-based tours like SOI, The ICE and Denis Ten's ice show in KAZ (hence their strong friendships with people like the Japanese skaters, especially Takahito Kozuka and Kanako Murakami, and Russian skaters like Elena Radionova and Trankov/Volozhaar) and their increased efforts on social media (i.e. Arden Cho and the other LA-based YouTubers). And it seems like when they're in Detroit and not training, Maia spends a lot of time with people like Alissandra Aronow (
https://www.instagram.com/p/BW3aiFyADS2/?taken-by=alissandra.aronow), another ice dancer that trains with Marina and as chapis pointed out, with Alex. And I think they have a nice relationship with Meryl/Charlie (
https://www.instagram.com/p/BbAkwkslk2Q/?taken-by=maiashibutani), but it's just that their schedules don't intersect much.
I don't think it should be read that they're loners among skaters -- they just simply put more time relationships outside of skating, or more specifically among skaters competing.
[also this is all based on looking at instagram pictures, and we all know that doesn't always give a full picture]
FWIW, Tessa Virtue doesn't post a lot of photos of a lot of other skaters other than Scott.