You are right, it would look much better bent. However, the radius on a bent tube for the roll bar that would allow the canopy to clear is too tight to be strong.
If we lower the bar to get that radius where it has the required strength would lower it below the height of the average pilots head – leaving it useless. The roll bar may not look as nice the way it is, but it is strong and tall enough to do the job it was intended to do – protect your cranium.