Because making a decent GUI is harder than making a decent TUI. Also TUIs give you some nice things for free like working over SSH easily, but I suspect the lower dev effort is the big thing.
They are both not easy to make great, but with TUI you have way more constraints than with GUI so you can make something decent quickly and focus on important interaction and not on pixel-perfect button alignment.
Windows 98-XP GUIs were the best for such cases: there were clear design guidelines, everybody used native components, and GUI designers in IDEs were practical.
Presumably preference of their users. From what I know, other than for cursor, the GUI interfaces are less popular than the TUI ones. Personally I also did not expect that I would really like the TUI experience, but it's hard for me to switch away from it now because it has become so central to my workflow.
It's easier to ship a TUI app cross-platform, the constraints around UI and state are often simpler, and some good libraries/frameworks (e.g. [1][2]) exist to make a modern-looking UX.
I considered a GUI for a small Python project of mine, but couldn't find anything quick, simple, and portable. I ended up opting for a TUI with a few ASCII art boxes.
This post has aged like milk given the rollback. In the amount of time it's taken them to fix it, including lobbying xterm.js upstream and telling users "use a modern terminal emulator", you'd be hard-pressed to convince me they'd have burned more goodwill with paying customers than they already have if they'd quietly switched to alt-mode. It's a downright embarrassing bug for such a high-profile company.
Windows 98-XP GUIs were the best for such cases: there were clear design guidelines, everybody used native components, and GUI designers in IDEs were practical.
[1]: https://github.com/charmbracelet/bubbletea
[2]: https://github.com/Textualize/textual
Claude Code seems neither quick nor simple