A bit like saying I bought a magazine which I then gave my neighbour to read so the newsagent should prosecute him because of their loss of income

No. It is not.
I seem to make this point on here from time to time but it doesn't seem to have any effect on people expressing their own 'ideas' as if they are fact.
You are making a fundamental error in confusing Contract Law with property Law or consumer Law.
I may buy a sandwich, a Bentley, a magazine, or a mobile phone, and give it to you;
I may not enter into a Contact for Life Insurance, professional training, dental care, education or Employment and give them to you
The distinction which maybe should be clear is not whether you have paid for something, but whether a specific agreement with a specific person has been formed - a
contract. A non-transferrable contract. A railway ticket is evidence of a contract.
We shouldn't confuse consumer goods (which can be exchanged at will) with personal contracts (which are based on the specifics of the people concerned). If you pay for someone else's dental care do you expect their root canal work done on your teeth?
In terms of rail travel, this principle was clarified long ago. The classic case is
Browning v Floyd [1946] KB 597 in which Arthur Floyd, the husband, actually had a valid ticket in his pocket, but instead presented his wife's return ticket, hoping to use his own on another later occasion (on Appeal, his Offence was found to have been captured by three Acts of Parliament and one Railway Byelaw, and Doris Floyd, his wife, was found guilty of aiding and abetting her husband in two of those offences and one Railway Byelaw in her own right). Just because they had paid, you might think that they had fulfilled their obligation. But you would be as wrong as they were.
A little before then, was the incident of Michael Keohane who passed a valid ticket to Lewis Greaver and was found Guilty in
London Midland & Scottish Railway Co v Greaver [1937] 1 KB 367, or long before then, in
Langdon v Howels (1879) in which he used another person's ticket; these cases have been the basis for securing prosecutions in hundreds of subsequent incidents of passengers transferring railway tickets - tickets which are clearly marked 'not transferable'.
And as for not having seen the small print, even poor Mrs Mary Thompson who couldn't read, and therefore didn't read the exclusion from liability on the ticket which her neice had bought for her, wasn't able to argue that the company hadn't made the conditions clear - in
Thompson v London Midland & Scottish Railway Co [1930]. How's your eyesight?
These fundamental distinguishing characteristics of Contract Law are not about to change because you believe that attempting to transfer the benefit of a Contract is "a bit like saying I bought a magazine which I then gave my neighbour to read".