Alligators?

What is an alligator? In radio terms it's a person who is all mouth and no ears. If we apply the same idea to radio stations (not people), do we have alligators on WSPR?

On a typical overnight (midnight to 8am my time UTC+8) session on 40 metres, I will hear around 6 Europeans and a small handful of North Americans. Yet most nights I am only heard by a small few of those stations.

What does it say about a station's Rx capability (including environmental issues)? Where are the principles of reciprocity when I hear a 0.5 watt signal from 14,000 km away and my 10 watts is not heard in return?

The reciprocal principle says that, all being equal, two stations should hear each other the same, however it's clear to me that all isn't equal.

It's not sour grapes driving me to write this. I just wonder why a station with a Tx antenna good enough to make a 0.5 watt 14,000 km trip, can't receive a signal much greater in magnitude over the same distance/path. Are the paths really one-way so often?

I think I'll take an aspirin and lie down for a while - too much thinking :)

Post-Edit:
I must be fair, however, and admit to having a bloody good receive antenna - it's a loop made from 80 metres of wire suspended about 11 metres from the ground. God and I planted some trees a long time ago making perfect supports for such an antenna. The closest corner of the loop is about 20 metres from the house, so the feedline to the house (20m out, 11m up) is a home brew parallel line, into a 4:1 balun at the house, and a coax the next 15 metres to the shack and ATU.