I still meet a surprising number of people reluctant to get a 16-25 railcard, usually saying they don't get trains regularly enough - and i urge you if you have any ability to do so, that it is nearly always worth it. Even one long-haul train in a year (i.e. London to Lancaster) can make a 16-25 railcard worth it as those long trains scale up in price massively and 1/3 is a huge amount off that cost. And if you regularly make shorter journeys, it will still save you money over the span of a full year.
There is a 26-30 railcard which is similarly worth it if you're someone that travels even semi-regularly, in my case I don't live in the same town as either of my parents so i'm always travelling at least semi-regularly, even if I don't have other specific plans. The only difference being you're locked into renewing them every year instead of the option for 3 year-long 16-25 cards (at a discounted price).
And mature students can be eligible for 16-25 railcard while in full-time education (yes, even if you're over 30!)