Yes, just nobody has implemented it. It's kind of a pain. Also it brings up the question of whether GDB ought to implement a terminal so you can debug curses applications inside the TUI, which is even more of a pain.
No-one maintains the Pascal support in GDB. In fact, I think the test suite doesn't even run any more (at least for me, FPC seems totally broken). This is an area where a volunteer could make useful progress pretty easily.
Rust support landed in gdb 7.12 (released October 2016). It has some rough edges; and some missing spots (mostly caused by insufficient debuginfo).
I'm working full time on Rust debugging now. My basic plan is to write a Rust plugin for lldb (WIP branch https://github.com/tromey/lldb/tree/rust); then update LLVM, rustc, lldb, and gdb in sync to add support for missing features.
I'm interested in bug reports and other constructive feedback.