It's also easier to develop and deploy than a traditional GUI app.

I actually prefer TUIs, unless a GUI is absolutely required.

If you just make a TUI-style app in graphics mode, is it really that much harder? Granted, there's a bit of boilerplate for setting up a drawing context, and you might want to make your own minimalistic drawing framework (because windowing toolkits might be too much), but apart from that I'm not sure it's hard. And you even get image display for free! Plus an easy upgrade path for example for minimal mousing, keyboard combinations, etc.

I build complicated GUI apps for a living. I still prefer the simplicity of a TUI.

They're also generally faster to launch and surf (unless you're doing a lot of updates, which requires double buffering and is still very dependent on your terminal's performance).

You also have to be more clever to pack information in a smaller section (typically < 100x100 character space), and you avoid unnecessary graphics that are distracting.

Yeah. Thinking about it, the appeal really to me is that I don't have to give a shit about fonts/colors/etc. I only care about the data. I'd live my entire life this way, if I could.