Firstly, many websites have been using frames since the 20th century. It's not a new phenomenon.
Secondly, it's quite possible that that's the only web browser that they have available to them. You've probably never heard of Charlotte. Last time I used it (a while ago admittedly) it was the only browser available for the system that I worked on and it had no frames support. (It had no graphics support either - text only - graphics could've been added but it would've been a lot of work. Like most "free" browsers it needed support - no sponsorship for this was forthcoming hence no development.)
Thirdly, I use one to see how the website looks for people who have to use browsers without frame support. Similarly I run the work websites through the various colour-blind translators - the results can be quite enlightening.
Quite. Some people use them for scripting purposes (like when the dumb vendor doesn't provide an API to their product and the only way you can programmatically do something is to scrape the screen (currently fighting that one at work) - presonally I hate the things and push to get APIs from people). Quite why they'd want to script a model railway website though is beyond me :-)
We've already had the discussion about braille keyboards and things methinks.
-- Rod