I think you're confused on the meaning of "open source". Quite simply, it means that you've released your source code into the public domain, presumably with some kind of license (i.e. the public can use it to make derivative works or a commercial product, or the public cannot, etc). Open-sourcing your product doesn't mean that you have to take code contributions from anyone else.
As was previously stated, the reason people would like you to open your code up is because you're an "unknown quantity". I wasn't trying to be rude, just stating my opinion based on experience that uptake of your software will be considerably less with closed source *because* you're unknown on these forums. And for goodness sake, stop comparing your product to the likes of Apple or Microsoft - these are multi-national multi-billion dollar enterprises.
By the way, I'd most certainly try your product if it were opened up. I think it has larger and far more reaching implications than itself, which could serve the greater community. For example, perhaps the off-spin of an API library for inclusion into other programs in the future.