I imagine if they didn't exclude such, you'd have a rash of LLPs turning into C-Corps; not sure what other negative consequences they're hoping to prevent.
A subsidy to small businesses that didn't exclude service businesses would have the effect of making more people want to work for service companies. Which is fine, except that they produce negligible exports. If you're selling lightbulbs, you make money in India by selling them there; if you're a lawyer, the way you make money in India is by hiring an Indian lawyer in India, and somehow convincing this lawyer to give you a fraction of his billings (so most of the money stays behind).
Given the potential trade deficit problems, I suspect Obama wants to focus on subsidizing businesses that can export.
Also, the income of a service company is mostly going into the pockets of the service providers, and if those service providers are well-paid then they're more likely to save their marginal dollar instead of spending it. So from a Keynesian point of view, this is not the kind of business you want to throw money at during a recession.
Looks like we're out, guys..