I have a couple theories about just why social bonding is so integral to a Cybertronian that having a roommate is essentially necessary for mental health and. Honestly I think the best I’ve come up with is that “social bonding is literal networking when you’re a living computer.”
We have SO MANY points of interaction in canon! Not even including things like music and other forms of media, but just things to facilitate social bonding: face to face talking, body language and facial expressions*, comm links, EMF signals, direct hardlining, sparkbonding, literal in-canon forms of familial unit building (trine! gestalt! deployer and cassette! mentoring! conjunx! amica! crew! faction!)
By design, a Cybertronian is in constant communication with their entire environment, every other living being around them. Status, health, information, ALL OF IT, it can be communicated with something as simple as a burst from an EM field (though I’m sure there are also rules of politeness around what signals you can give off and at who).
Cybertron itself, the literal freakin’ planet, is capable of communicating with Cybertronians. Cybertron is the smart home hub of the entire species.
Till All Are One isn’t a comfort or a religious ideal so much as it is an actual physical possibility enabled by how Cybertronians are capable of networking! Cybertron and her offspring make a million, billion bright points of computational power!
(*social behaviors and expressions largely only develop in species with the need to cooperate and bond to ensure survival)