Some entrepreneurs are willing, but most funders are even less willing. A pitch that you've found some important, but uncommercialized, recent scientific or technical advances that you see a market niche for can be well-received. A pitch that you're going to make some significant scientific or technical advances as part of your startup's R&D effort is usually seen as way too much risk: a VC does not want "major scientific advance" to be in your critical path. The result is that the significant R&D has to happen elsewhere (often academia) to produce the stock of not-yet-commercialized results that startups can build on, rather than being produced by the startups themselves, since they can't have significant/risky R&D in their critical paths. Even Google, for example, only got funded after significant R&D work had been done by the founders in grad school.

Seems less true in biotech, where VCs are willing to fund substantial R&D budgets, perhaps because the [breakthrough -> patent -> license] ecosystem is better established there; the tech startups using the breakthrough/patent/license pipeline seem to verge on patent trolls more than real R&D outfits.