It shouldn't do anything until the user has told it where the files should end up. It's an unpackaged program, there is no sane place to put it that doesn't have a high chance of conflicting with something else.

That's only due to a lack of standardization. I think a default install to a vendor-specific directory under /opt is a sane place to put it, and there's a very low chance that would conflict with something else.

But sure, absolutely, an installer should prompt the user for an install location, and I think a default under /opt is probably among the best defaults possible, if we consider installing outside $HOME to be reasonable.