There are technical reasons, but as ever the real underlying causes are incentives. Companies realized that the OS is a profit center, something they can use to influence user behavior to their benefit. Before the goal was to be a hardware company and offer the best hardware possible for cost. Now the goal is to own as large a slice of your life as possible. It's more of a social shift than a technological one. So why would a company, in this new environment, invest resources in making their hardware compatible with competing software environments? They'd be undercutting themselves.
That's not to say that attempts to build interoperability don't exist, just that they happen due to what are essentially activist efforts, the human factor, acting in spite of and against market forces. That doesn't tend to win out, except (rarely) in the political realm.
i.e. if you want interoperable mobile hardware you need a law, the market's not going to save you one this one.