There's an angled set of train tracks near my house that most people will take a curved path over in order to cross perpendicular to the tracks, but I usually just bunny hop twice (@ about 18-20 mph) to get the front wheel into the middle then over the 2nd rail.
It's mainly because I'm too lazy to swerve, and I also don't like swerving with other riders also trying to swerve at the same time...

I usually use a hop if I come upon a stick, rock, hole, etc. too quickly to react by going around it. It's also a bad idea to swerve in a group because someone could run into you (or you into someone else).