How is this question a Must be true ?

This is a surprisingly hard to prove answer for a most strongly supported question. To start out, I'd note the difference between a question like this that's asking which is most supported, and a true must be true. For a true must be true, we need 100 percent certainty that the right answer is right. For a mss question like this, I think it's ok if we're only at 98 percent. And here, we're barely at 98 percent. We know that in some other similar companies, employees continue to use the old software, which shows they prefer that one over the new one. However, there still could be some systematic difference between the company in question and the ones the author references. This is a real cause for doubt, but ultimately the argument does strongly support (but not prove) that it's very likely some people will prefer the keep the old one, based on similar cases in which people preferred to keep the old one.