Just realized that the whole bids for connection thing of relationships applies to friendships.
A bid for connection is somewhat self explanatory; it's a 'reach out' to someone, in casual conversation, where the other should respond. If they don't, they've rejected the bid, and if this happens recurringly, it may lead the 'bidder' to feel neglected, and their relationship may strain.
The classic example is somebody looking out the window, seeing a bird and saying so (the bid), and the other person either ignoring them (rejecting the bid) or answering in whatever way ("oh what kind of bird?" / coming to the window to see; accepting the bid).
A healthy rate of bid acceptance is at least 4/5. Some can slide, but bids need to be overwhelmingly accepted, on either side of the relationship bridge. Otherwise, resentment may build and degrade the connection.
I learnt about this through the lens of life partners / romantic relationships. But I just realised today that it also applies to friendships.
Posting on your Instagram is a bid for connection. If your closest friends don't interact with your post, when you know they've been active, it may feel like a bid rejection. Saying something in a discord chat is also a bid for connection. If ignored, it may come across as a bid rejection. Where this to happen consistently, without other bids for connections getting answered, the friendship may feel like it needs a reevaluation, feeling grown apart or distant.