Wait, what? Peter, have you gone full derp? Not at all. Ask yourself this: why did Bruce Wayne never adopt Dick Grayson? It was clear that Bruce loved him (like a dad, smart ass). But Dick was never more than Bruce's ward. Why? Why not just make everything official?
Because it would have reopened an investigation into the death of the Flying Graysons, one I suspect Bruce Wayne was responsible for.
Let's think about Bruce Wayne. Bruce Wayne sees his parents killed and decides to become a crime fighter. Part of this means leaping around buildings, swinging through the air, and so on. This is acrobat stuff.
And where do you go to learn acrobat stuff?
You go to acrobats. Like the Flying Graysons. Who were about the same age as Bruce.
The key thing here is that Bruce was heavily into puberty at the time, as presumably was Mary Grayson. My theory states the two would probably have had some teen-age fun, and probably an accidental pregnancy.
Did Mary know too much about Bruce and what he was doing, or put the peices together when word got around of some guy dressed as a bat leaping around Gotham City? Or was she after an extortion racket, either as the Batman or to get the millionaire playboy to pony up some dough for the kid? Maybe John Grayson was the key figure, angling for revenge for Bruce boffing his wife. The fact is, when the Graysons fell to their death, Batman (not Bruce Wayne, but the goddamn Batman) was right there, offering to take Dick under his wing, nailing a mob boss and pinning it on him.
Bob Kane drew Bruce and Dick looking like they shared a family resemblence. And the timing is suspicious. Why would Bruce Wayne bring his Bat suit to a circus act and change into it so quickly to offer Dick his vengeance? In order for a formal adoption to be made, they would have looked into the history of the Flying Graysons. And maybe found out too much about Bruce Wayne/Batman. He either did it to cover his tracks or shut down an extortion scheme.
And that's my theory.
What do you think, sirs?