Why does a pilot want to hold a Squawk Code when leaving Class B airspace? I was listening to liveATC today... Controller clears this guy into the class B for a transition and throws him a code. Some time passes and the pilot has now transitioned the bravo and is leaving the airspace. The conversation goes roughly like this:

ATC: N12345 are you going to want a handoff?

N12345: No sir but we'd like to hold our code

ATC: Okay, N12345 you are leaving my airspace, radar services terminated, squawk VFR, frequency change approved, see ya!

Now, I guess this boils down to two questions:
1) Why would he want to keep his code if he's not being handed off to another controller? What difference does that make?
2) Why did the controller still say to squawk vfr, even if the pilot wanted to keep his code and the controller said that's fine? Didn't the pilot go against an atc order by keeping his code and not squawking 1200?

I'm a sport pilot and have yet to use flight following (nor do I have my class B endorsement), so maybe I'm just missing something due to lack of exposure!
The pilot means: I'll be back again, so please don't assign this code to someone else.

Less workload for a pilot going in and out of class-B airspaces, and less hassle for the controllers, so they don't keep assigning a different code to the same plane.

The pilot will switch to the VFR code (1200 in the USA), and then use the one he's written down and used earlier for future passes.