There is good reason: it's bad for software businesses. Even if you had a turnkey solution (it doesn't exist yet) to self-host emails & stuff, the companies se

There is good reason: it's bad for software businesses. Even if you had a turnkey solution (it doesn't exist yet) to self-host emails & stuff, the companies selling it wouldn't be able to get good search engine rankings. The web giants have no interest in solutions that don't require them to host your data (so they can serve you advertising or hosting plans). Even small shops are usually based around a Service As A Software Substitute (SaaS) business model and don't give a crap about you not depending on them when you start their application.