Admittedly, after a decade and a half in the JLA together, several world-ending events, a couple apocalypses, and a shit ton of obsessively thematic supervillains... Clark probably owed Bruce more than he could count definitively. A yellow sun powered Kryptonian was a force to be reckoned with-- but a guy from New Jersey with no sense of self preservation, a lot of money, and an undefinable rage that he refuses to go to therapy for? Yeah, Clark wasn't ashamed to admit that The Bat had saved his ass in more than a few fights.

So, of course, when Bruce called asking if they could take his youngest for a few days while Gotham recovered from a major incident with Scarecrow ('Better air quality', he said, which... Was true on an objective level), of course Clark agreed-- and, seeing that cheeky Boy Scout smile made sure that Lois agreed too.

So, here we are, a few days later, and you're standing at their doorstep, bags in hand, squinting in the sunlight.