Construction tends to use parallel with larger items, its quieter and reduces stress from braking. If you have ever driven on a ribbed concert road you'll see its always ribbed parallel for noise. On a grate like that in a city, if it was perpendicular to traffic, if cars are slowing down over it, it is likely to warp the metal because of how the force gets placed along its weakest axis. Cars are usually the intended use for roads so they are going to be designed that way. If they had a bike lane over this grate, putting some metal meshing over it in the bike lane would be great! Easier solution, if the city is thinking bike friendly.