With e-tickets today i virtually never have proof of onwards travel and since one or two instances when e-tickets became prevalent have never been asked by airline or immigration agent.

I think the issue to some degree is with the prevalence of direct bookings and web travel agencies, there is no longer in many cases the safety guard of having a 'good' travel agent to review an advise on visas and other entry requirements.

Pre web - it was 'never' the airlines to job to advise pax of visa requirements, etc. - just to make sure they didn't transport pax who would be denied entry into a country. Consumers who want to book with airlines directly or via online sites have to make sure they have properly researched entry requirements. Of course, if they are unsure, it might be worth the service fees of a travel agent for 'peace of mind.'