Obsolete Jobs

We're all familiar with jobs that disappear because of technological advance, where mechanisation on farms replaces labour, or now where the internet may make many real estate agents and travel agents redundant.
And, subsequently, the world changes and workers move from agriculture to industry to services.

But I'm wondering about the jobs that have disappeared without any apparent technological change. Once all lifts had operators, yet I have never seen an operator in my life. There is no mechanical button pusher though. Through films and novels written before my time I know of petrol pump operators, who would refuel your car for you, but I have only see this once (in the affluent suburb of Rose Bay).

I'm sure there are many other examples. In these two cases, we merely do ourselves, as the customer, what the worker previously did. It seems reasonable that as wages have risen across the board, the cost benefits of employing workers like this changed enough to entice employers not to hire them anymore.
But it's difficult for me to think of a time where the relative benefits would ever outweigh the costs of wages. Maybe in the very early days people would have been scared of the technology, and this was the only way it could be utilised, but I can only imagine this fear lasting a matter of a year or two. Why did it take so long to realise that people were perfectly capable of putting a nozzle in a tank, or even more simply, pressing a button on their own. The minor inconvenience this represents would be costed less than the higher prices required by paying these workers by most people, even with 1950s wages.

So really, the question may not be why they disappeared, but why they lasted any time at all.