Why would you assume that the navaid is ALWAYS beyond altitude and
distance limitations? Surely there must be *some* approaches where you
could be coming in at nearly the right course and altitude if you were
cleared directly to the navaid from a nearby intersection or airway? I
was going to say the NDB 28 at PEO from PTAKI intersection, but realized
that because the navaid is on the field you wouldn't know when to descend
to the MDA without some independent way of knowing you were within 10
miles of the field.

Being cleared direct-to inside an IAF is not in accordance with air traffic policy. If
they want you to go straight-in and in the process bypass a pertinent IAF, then they
must vector you to "final" in accordance with 7110.65, 5-9-1.

Otherwise you, as PIC, are required to begin an IAP at an IAF. If that IAF is followed
by NoPT routing, then you go straight-in. If not and a course reversal is charted you
do the course reversal.

References: FAA legal interpretation from November 1994 (on Summit Aviation CD) and
related AIM material.