Alex, here in Canada strobe lights are not required by law to fly (as long as you have a beacon, nav lights, landing lights... etc) although strobe lights significantly increases an aircraft's appearence at night, and are now very popular from GA's to airliners. It is actually a good practice to turn on your strobes when crossing a runway, it is not law, but good practise! I turn them on when I cross any runway. You'll get noticed much more easily by someone that made an error (ATC/Pilot) ex: if you have an aircraft that is mistakenly landing on a wrong runway, he/she might notice you before it's too late. Go to any big airports and I guarantee you'll see some pilots turning on their strobes when they cross any runway.
Remember to turn them off as soon as you are again clear of the runways as it just becomes a nuisance on the apron.
Happy Flying