EWR-IAH (and, i'm told, IAH-SEA) sometimes skips elite boarding, due to travel schedules. At beginning and end of week, this flight can be 90% elite; elite boarding would be worse than row by row.

A few times at backwater hubs at odd hours they've overlooked calling elite boarding; I just walk to the blue carpet while they're boarding from the rear. Only had to say "elite access" once; generally they figure it out. When this has happened...looking at all the Kettles it was very safe assumption that I was probably the only elite on the flight.
(Let all the kettles go first on an RJ? With their three oversized carryons and extra jackets? ha!)

Worst "no elite boarding" experience: One time at Narita, the gate crew had almost no english and was very confused in general (I think it was a substitute crew). After first class, they called "ladies and gentlemen...we board now!"
I think that was a 747, and the NRT-LAX run (which is FULL of disney tourists and snifflly noses...avoid this route).
God what a mess that was.