Well yes, but it's not quite as straightforward as that.
Quite, this thread isn't about the practicality of buying tickets but the attitude to buying tickets.
There are many who take a great deal of trouble to ensure they've ordered their ticket well in advance online. They've probably gone to their local station to pick them up, also well in advance. When the TVM was out of order they've uttered a silent curse and returned the following day or gone to another station. They are one extreme.
The other is the daily commuter who stands near the front door in the front carriage. Or when the guard comes down the train they're apparently asleep or so engrossed in their mobile device as not to notice. More often than not the guard will walk past. Some do have tickets, of course. These people are chancing it but are likely to avoid payment on most days with most Northern trains into all but a small number of stations where there's barrier control. They are the ones that Penalty Fares may catch.
In the middle are the ones who know exactly what they're doing. They've obtained a promise to pay ticket (so they've demonstrated ability to use the TVM, and said they haven't a valid card with which to pay) and have the cash ready to pay if challenged. Many of these should be buying season tickets* but playing it this way are 'saving' more money. They are protected against any penalties. Yet I'd bet a large sum that at least 95% have a valid card they could pay with.
I'm sure they may think they're not fare dodging and that it's the TOC's problem not theirs. It is! But they are deliberately evading payment, legally
Can I think of a better system? No, but more focused enforcement might be effective.
I'm quite used to seeing the guard issuing tickets to passengers who've boarded Northern's stopping service for Manchester at Sheffield, a station with a booking office and a dozen or more working TVMs.
Northern have got wise and users may get a surprise when they meet 6 revenue protection staff at Dore on an evening. I sense more tickets are being bought.
*The season ticket option wouldn't apply for many from my station. Some don't work 5 or more days a week. We have an excellent commuter service into town (4 trains in about 35 minutes) but only hourly out again in the evening so many make other arrangements.