Cherchez la femme
I absolutely loved this part in TAB, and even though this takes place in Sherlock’s mind palace it’s really good to see how it’s always Mycroft and Greg who’s with him and helping him.
I get the feeling that since John got married Sherlock is under the impression that John has other priorities and responsibilities namely Mary and their lufe, which is why they left.
But Greg? He is always there and even though Sherlock’s ideas and antics are weird and insane he still sticks around. He believes and trust Sherlock enough to be there.
Sherlock knows he can always rely on Greg and Mycroft on being there.