As a vendor, dealing with hacks, jailbreaks, and other such things is remarkably expensive. Consumers (not developers) wind up installing these things without understanding the implications of what they're doing. The OS breaks, the applications break, things go haywire, things go bad. The hardware vendor, the OS vendor, and the application vendor all take the blame and have to deal with the support costs. We get support e-mails all the time that can be traced to iOS jailbreak-induced issues.
It's a massive pain in the neck that, understandably, a vendor just doesn't want to deal with.
Moreover, as a consumer, it's incredibly wasteful to be spending so much time on trying to break into undocumented systems that the vendors just aren't interested in supporting.
Instead, I want to support vendors that provide more open platforms for a more premium price. It costs more to produce an open, supported platform, and I don't mind paying a little bit for an Android development phone that allows me to experiment with OS-level work, or something like the Ubiquity RouterStation Pro[0] as an alternative to consumer wireless routers. The advantage to me is that hacking the device is supported and I don't have to fight with a consumer manufacturer -- a company with very different priorities to my own -- to do it.