I have been thinking about research from Nielsen Norman Group about the usability issues faced by over -65s
The over-65s are demographically the last group to be spending time online, and if they behave like the other age-groups, sending time will evolve into spending money.
We are all on a journey to poorer eyesight, poorer motor control and worse memory - for some people over 65, these have become significant barriers to web use. In addition, the over-65s Nielsen Norman studied showed more willingness to blame difficulties in using websites on themselves, and so more inclination to give it up as something for younger folks only. Anecdotally, becoming less confident about new experiences is another common issue about aging (though of course individuals vary hugely).
With each year that passes, however, there are more people in the over-65 age group for whom the Internet is not so new. I think that is an important point. To illustrate it, here is a table (pdf file) showing how old you'd be now if you turned 65 in the year of some events from Internet history. The table also shows the approximate percentage of the world population online that year. For example, you're 71 now if you were 65 the year the first iPhones came out. If you retired at 65 and got yourself one of the first Android phones, you must now be 70. If you are 85 now, you were 65 the year the Mosaic browser came out (arguably the ancestor of all modern browsers). But if you used it age 65, you were highly unusual - among less that 0.4% of the worlds' population online back then.
It's easy to see how specialised and niche the Internet was at the time current members of the over-65s joined that cohort. There's nothing magic about the number 65, of course - people don't necessarily start behaving differently, or suddenly lack confidence with new technology. But I think it is worth remembering how comparatively recently everything has happened.