Why say source code is available with an ArXiv paper when it is not? I sometimes come across ArXiv papers where the authors claim the source code for the project discussed can be obtained, but on checking the link provided the source code comprises no more than a place holder. So the code is not available, and on subsequent checking months later (in case the authors were in a rush to publish the paper before the code was quite ready to release) the code is still unavailable.
Now I understand there is no obligation to provide source code with commercial potential, unless maybe the project was subsidized with public funds. But what do authors have to gain by claiming it is available when it is not actually available?
There is no advantage to claiming the source code is available and then not doing that. All it will achieve is irritating the really interested readers.
The most likely reason is it’s a simple mistake. Something like they wanted to do that but forgot. Or other reasons, maybe department policies came up that prevented the author from doing that. Or maybe the author found another more suitable place to publish the code and forgot to update the link in the paper. Or...
The simplest solution is to contact the author directly.