Furthermore, if you broke down and your vendor wasn't available, you'd have no hope of being able to fix your car yourself, or even of getting a local mechanic to help you. Open interfaces are the only kind that will serve you in the long term. Anything else is just serving the system vendor. Of course, sometimes you just need a phone that will only be used to call one person. You certainly don't want to have to understand how your car works just to get in and drive somewhere.
Proprietary systems are a dime a dozen, and in some limited cases can be useful.
But for serious work, adopt a long term strategy. Get an Open System. For a system to be Open, it must be based firmly on standards which are developed and have been adopted by recognized standards organizations. The overwhelming majority of work an Open System does must be accessible through such interfaces and protocols. Furthermore, an Open System must have explicit provisions for expansion through well documented, non-proprietary means, with minimal impact on the system as a whole.