Investors want the big ideas, though they don't want to pay for them. Tesla Motors and SpaceX would have never of started if Elon Musk didn't have money from PayPal being sold. This is why unless you know you'll have the funds to work on the big ideas yourself, it could be time and energy invested that will leave you not benefitting from it. Really it comes down to learning to enjoy what you're doing in the moment, and be working towards something bigger. It helps knowing what that bigger thing is, though I imagine not always necessary.
And consider how even Tesla started with the Roadster, and then the Model S- targeted at small demographics. Consider how SpaceX is working on reusability of rockets.
They might be "thinking big", but they're also "working small". They have to.
