What is the benefit of being solid with Amnon Duul (Travel Hub)?
As well as being useful in cases where fugitives or passengers die and you have a job which requires a specific amount of them, there is another case where being solid with Amnon Duul can be handy.
If you start a job like Patience' Ranch Hand Recruitment which states

Pick-Up
Load Passengers, no limit.
Drop-Off
Deliver Passengers. Get paid $300 per Passenger.

but you have some of your cargo hold filled with other stuff (requirements for another job, parts, fuel or randomly acquired cargo) which you are able to offload on the way, then you can top up your cargo hold with more passengers so that you can earn more on completion of the job.