I spent a few years fare-dodging and couldn't have managed otherwise (it's not always easy to find a job within walking - or even cycling - distance of your home and moving house isn't that straightforward). I'm grateful that I was able to do it. Hell, I've even done it recently - and I really had no choice. It would take my life history to tell you why, but really, I had no choice. There's no doubt that I'd be costing the taxpayer (including myself) far more in unemployment benefit than in lost train fares if I couldn't have bunked at the time. (I do cycle part of the way, but it's too far to cycle the whole distance in the time I have).
However, I always accepted that if I get caught, it's only fair that I would have to pay the fine. Fare-dodging is allowed by the system (unintentionally), but so is punishment for that.
It's not cut-and-dried either way. To elaborate, at regretable length ...
The system is supported by taxpayers, and they benefit indirectly even if they don't use public transport themselves: by having people be able to get to work to keep the economy going, especially service people or others in low-wage industries; by reducing emissions; by increasing social mobility; by making high house prices spread out a bit further, and lessen the overall impact; by reducing road traffic for car-drivers; by increasing accessibility to work and cultural events for those who can't physically drive, which increases the pool of labour and increases the revenues of such cultural events, enabling them to continue; by decreasing the number of drunk or incompetant drivers: those are some of the benefits you're paying for, Cobblers, and anyone else who doesn't use public transport personally.
If public transport suddenly had no subsidies, everyone would soon be wondering why their streets weren't clean and the prét a manger were closed (the cleaners and shop workers can't get to work) and why the roads were even worse than usual (more people using cars) and why their Grandad could't get to his lunch club (because he failed his post-75 driving test and can't afford a taxi), and why most people with epilepsy are suddenly unemployed (because, legally, they can't drive).
All the same, the system still - economically and morally - should be supported additionally by those who actually use the system, through the fares they pay. It's not like there were no train fares before privatisation. We pay through taxes for the social benefits and a reduced personal cost to ourselves, but if we use the system we pay extra, because we are getting extra, personal benefits from it.
However, there are not enough systems in place to alleviate the high costs for those who can't afford them, and the costs, especially outside London, are very high. There is a negligible student discount within London, and while there is a discount card for people on certain benefits, it's a recent thing, the rate of discount changed a lot recently, and it still doesn't help those on low incomes who cannot receive benefits. Also, as far as I know, the discount card for people on benefits is only in London and local routes (on buses and trains) outside London don't give student discounts. I could be wrong about that.
The lack of ability to use Oystercards on some London train routes is a travesty. Quite often I've used the tube and buses, etc., often enough to upgrade to a daily travelcard, only to have to buy an extra paper ticket for a fair amount of money to make one train journey. This has even happened when the only reason I had to use the overland train is that the tube was fucked. Grr!
Paper daily travelcards cost a fair bit more and are intended for those who don't have Oystercards (namely those who don't live in London and don't support the transport systems even more through local taxes). They shouldn't be necessary for London internal routes. That is why, Cobblers, fare-dodging is more justifiable on those London routes which don't support Oyster. (Sorry for addressing you directly so much, Cobblers; you just brought up a couple of things which I thought I could answers to, although I don't disagree with your general POV).
Train guards do check teenagers more, in my experience, but that is for the good reason that teenagers are more likely to bunk. Though that's partly because teenagers are more likely to be poor, and many older teenagers have a low income
and no recourse to student/benefit discounts.
Softybabe - are all buses free for under 16s now then? I've seen someone else mtnion this elsewhere, but previously I thought it was just for under-11s. That's progress, if so
Honestly? I've paid tax for many years, and I expect to be a tax-payer for the rest of my life, even eventually a higher-rate tax-payer, and I wouldn't resent it at all if my taxes were a tiny percentage higher to allow for the tiny percentage who bunk public transport, especially those who, like me, had no other choice.