Centaurus,
Because "being more professional" is the mantra, and the "professionals" are all flying heavy metal and a 3 degree approach slope.
Compounded by the need to fly a "mandatory stable approach" (absolutely necessary in said heavy mental) and a glide approach is "not a stable approach" (from a CASA FOI who can't fly to save himself). A request for the reference to a "rule" that mandated stable approaches in light aircraft did not elicit any answer, not even a wrong answer. Apparently it is NTS ( Non Technical Skills --- previously known as airmanship) but when asked: "Show me where", "no answer" was the stern reply.
Personally, I have no trouble flying glide approaches as the preferred, in any light aircraft, indeed, even in a particular light twin I often fly an approach with barely above idle power --- that one gives abou a 5 degree approach.slope.
Again, apparently sideslipping is frowned upon, "because the heavies don't do it" ---- which, as it turns out, is wrong, most Boeing aircraft on an auto coupled approach sideslip across the wind to track the centerline at low level, except the 747, that uses a combination of sideslip and crab, due engine clearance, and there is no AFM limitation on sideslipping in any Boeing after the B707. -----and "it is dangerous" ??? ----- that from a CFI/Flight Examiner in a GA school.
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Tootle pip!!
PS: "Being more professional" apparently also requires never shutting up on the radio, never listening before hitting the transmit button, reading absolutely everything back including your collar size, and talking like a machine gun --- also known as the "pingya" system, if you make every call and read everything back, "they can't pingya".