Application scripting. Single file, low footprint, straightforward script/application interface. Can help with debugging.
Unless you know ahead of time your target audience probably likes it, or you're on a tiny embedded system.
You can see it embedded to provide a turtle-like graphics thing in this repository:
Forth-83 is not an implementation but a standard, superseded by the ANSI standard in 01994, though sometimes people confuse it with F83, which is Laxen and Perry's public-domain implementation of the Forth-83 standard. It came out in 01984. It runs on CP/M and MS-DOS, but the MS-DOS version is limited to a single 64-kibibyte segment. It has no facilities to support embedding it in a program written in another language.
eForth, if by that you mean Bill Muench's eForth, is written in, mostly, Forth, on top of a small assembly-language core. It also has no facilities to support embedding it in a program written in another language.
GForth is pretty usable and can be embedded, as documented in https://gforth.org/manual/Integrating-Gforth.html (which is down at the moment but will probably be back up soon along with forth-standard.org.)
I don't know anything about SwiftForth and picoForth, but so far ChatGPT is 1 for 3, so I wouldn't bet much on those either.
About GForth, it doesn't look convincing - actually the feature looks like an afterthought (like those libraries that have been teared out of a program, e.g. libCurl).
This use-case isn't well covered for Forth it seems, because the focus has always been mostly on the other embedding. That's why I'd recommend again the DIY route.