But if you are going straight in, say after setting oneself up at 1000ft AGL at 3nm, you have a damn good view (without twisting your neck off) of the whole airfield and any circuit traffic that is actually visible. If you see none, you can go straight in.
I think you'd probably have difficulty on most days, as you'd probably miss the traffic in the ground clutter. It is better to be slightly below circuit height
so the circuit traffic is above the horizon and much easier to see.
I still think though that a straight in approach is less desireable than a join from a base leg, though.