To be honest, the academic field is about the only field in which it perfectly makes sense to finish a degree, I mean, what else can you boast with if you have none?
The other three reasons are visa (proof of "ability"), wanting to work in government (if you really, really want that) or early-stage startups that need Ivy-League credentials for their investors, because they don't have anything else to offer.
Other than that, as a software engineer in the private industry, nobody will care about any of your degrees.
Well, I care, to some extent. Like many other things, it can be used as a filter. At the least, lacking other demonstrable evidence (such as open source or industry experience which can be confirmed by referrals), a finished master or PhD shows that someone is able to finish a non-trivial project.
The other three reasons are visa (proof of "ability"), wanting to work in government (if you really, really want that) or early-stage startups that need Ivy-League credentials for their investors, because they don't have anything else to offer.
Other than that, as a software engineer in the private industry, nobody will care about any of your degrees.