The railways would do well to look at the other service where not paying for it is generally accepted: software and digital media. The video games, music and film industries up to the late 2000s tried the most stringent, ridiculous measures to prevent piracy: Sony even resorted to installing malware on their legitimate customers' computers (BMG), supposedly to prevent copying but actually providing an unvetted backdoor into the system. Video games publishers would often force users to insert the game's disk every time they wanted to play it (so no listening to a CD and playing a game at the same time), and the film industry lobbied to make DVDs region-locked and Blu-rays encrypted with a proprietary CSS key.
All these measures were very easily defeated by anyone with the slightest motivation. What stopped piracy being so commonplace was convenience of buying. The rise of Steam, Netflix and Spotify meant that it was, for the first time, genuinely easier to buy media than to illegally download it.
The railways, right now, have not worked that out. They insist on more and more stringent punishments and opaque regulations, which serve to penalise infrequent travellers who have made a genuine mistake, whilst genuine deliberate evaders figure out how to trivially get around them, and share these tips on social media.
If the railways wanted to make it easier to pay than to evade, they'd install universal tap-in-tap-out (with the readers at multiple positions on every platform, not tucked in some obscure corner of the country end of the least-used platform, coughGWRcough), and perhaps a system like the "forgotten railcard" scheme: once a year (enforced by having to present valid ID), you're allowed to buy onboard. I suspect they wouldn't do this, because it would mean they couldn't squeeze the young and the elderly for hundreds in "admin fees" any more.