The obvious counterpoint being why should I, living on a minor branch line (well technically an intercity line between a capital city and the third largest city in the UK, but you wouldn't guess it) pay massive subsidies to a rail network which doesn't benefit me?
The taxes on my salary subsidise the commute of London stockbrokers on 3 times my salary. When I do travel by train I pay far more per mile than they do, and while the service is there, it's needlessly expensive, meaning more pressure on roads, more pressure on car parks
The arguments over paying in advance and interest free seem rather meaningless compared to the discounts. A £6164 Brighton to London ticket at 17p a mile, with a loan over the year at 6.5% to pay monthly, would cost £6400 (at 7%), putting the price upto maybe 18p a mile.