It's hard to think of a reason to refuse to publicly prove that your quantum computer is actually working if it really is, if it isn't it makes a lot of sense of course.
Concerning the purchases of Google and the US government: These are probably more like research grants for D-Wave, as the buyers expect that at some time there might come a working quantum computer from D-Wave, and buying a prototype (even a faulty one) puts them in a good position to be the first to actually get a working version, while helping the company to stay afloat. By the way, Google invested 200 million USD in a different quantum computing technology endeavour led by a UC Santa Barbara professor, which would make little sense if they already had a working quantum computer.
The value of D-Wave as a company is not only defined by their ability to build a working quantum computer though, as there could be significant value in the patent portfolio they built / acquired and in their expertise in building and assembling superconducting chips and systems, which are both highly non-trivial tasks.
Their way of communicating with the public is of course highly misleading, which is why many people in the scientific community have very little respect for them, as this is viewed as highly unethical and harmful behavior in science (but not necessarily in the business world).