I presume that the main reason for the introduction of eTickets is cost - and transfering that cost from the railway to the passenger - but I'm sure that there are others, such as data information management, too. Some passengers might like that, which is great, carry one using them.
But the most succesful businesses will want to make as many of their products or services as easy to buy for as many people as possible. If the railway wants to encourage passengers to use eTickets that's fine, but it shouldn't alienate those who don't. Costs are not just a P&L line between Gross and Net Profit, some need to be seen as an investment, or an ability to maintain and/or increase turnover. It's all well and good when some say that most people now purchase eTickets, but what they and the railway will never be able to quantify is just how much business they either lose, or never gain in the first instance, and the reasons for that.