What made you laugh and good luck with what?
Basically, because I don't know of anyone who doesn't do that to some extent.
It's not really a matter of laziness- ED shifts are incredibly busy and hard work, as L2D pointed out. You frequently get so busy that you don't have the time to do the paperwork- charting, checking on orders, discharges, talking to consultants who come down 3 hours after you called them, etc. You just see patient after patient, then a trauma comes in and you're busy and you get backed up again, etc. Many (most?) ED docs, at least in academia and busy community ED's, don't eat at all on shift- no time.
Because of this, most ED doctors I've seen myself don't leave their shift on time, ever. Generally, with sign-out to the next attending and finishing up all that paperwork that's accumulated during your shift, most of the ED docs I've seen leave an hour- hour and a half after their shift has ended. Some places overlap the last hour of your shift (so say, you're working from 6am to 4pm, the next guy comes in at 3pm) so that you have time to sign out and the next attending can pick up your loose ends- but many places don't have that overlap.
This means that, out of necessity, you have to triage who to see toward the end of your shift. If it's something super simple and quick that doesn't really require someone to sit around waiting for labs to come back or radiology to take you to a scan etc, great. That can be knocked out in a half hour, no problem. But anything that requires a big workup or consults to be involved or procedures (an LP to rule out meningitis, that kind of thing)- picking that up in your last half hour is just crazy. Sure, you can sign that patient out to another attending a half hour later, but what's the point? Maybe that attending would do a slightly different workup, and you run the risk of missing something in your sign out, like an allergy or something, that the new person would have caught by taking the history him/herself. During that last half hour most pick up the very high acuity stuff because someone has to, and the really simple stuff that you can discharge 10 minutes later- nothing in between. It doesn't make them bad doctors, it's just that after a busy 10 hour shift, having to stay 2 extra hours because neurosurgery hasn't come down, or you have to do an LP on a child and there's no one there to do conscious sedation is just a giant pain and unnecessary. If the patient can wait for a half hour to get a fresh attending who can follow him/her from history to dispo, it's in everyone's best interest.