"The legislation from the AIP enroute (25may08) is shown below
57.3 Circuit Height
57.3.1 When operating at non−towered aerodromes, the following circuit
heights are recommended:
a. jets/turbo props/high performance aircraft, 1500FT AGL;
b. typically single engine piston, 1000FT AGL;
c. ultralights with a maximum speed of 55KTS and
helicopters, 500FT AGL.
NOTE: High performance aircraft are those that have a normal
downwind speed of greater than 120 knots."
Theres the critical word in that paragraph. "recommended"!!!!
So if the pilots that are not flying at the 'recommended' circuit altitudes have in fact read this chapter in AIP/Jepp then they are obviously taking the word recommended quite literally. Or they just havent read this and are just flying at 1000' as per the old days.