-[small companies] even if you bought them a developer, it would impede their ability to be agile and pivot and iterate as they try to find something that works. It's hard enough to get them to support Android in addition to iOS, but getting them to support WP or BB10 is even harder
-[big companies] don't need the money. Or would ask for outrageous fees (some companies have asked for north of $20 million, even for faddish apps)
-[big companies] have an existing solution to do cross-platform development for iOS and Android and it's not worth it to redo it to add WP/BB support
-[small companies] complete lack of familiarity with the Microsoft stack.
-pressure from Apple or Google (usually Apple). I've had cases where a company gets favorable placement in the app store or in a commercial, or placement on the demo devices in a retail store and planned Windows ports are put "on ice" because they don't want to jeopardize their relationship with Apple (which of course has reserved the right to be as capricious and arbitrary with its app policies as they like)
-personal dislike. Believe it or not, some companies are run by people who just have a personal dislike of BlackBerry or Microsoft that is so strong that they'd rather spite them than add to their customer base. It's incredibly immature, but nothing we can do about it.
At least three times now in the past month someone has recommended an app to me an sure enough...no blackberry option. Android and iOS only.
What I don't understand is why they don't force popular apps onto their platform. Even if no companies are jumping to develop for Blackberry, pay them to do it. Get them onto your platform with no cost on their end. Pay for ongoing support if necessary. App coverage is absolutely crucial and at this point, with BB10 being what it is, I'd say app coverage is now the #1 problem for their phones.
They've gone pretty far down the crap slide now. Maybe they've given up.