The capital outlay required for pretty much any hardware product is enormous (compared to software-based products). Besides needing to sustain development effort to comply with emissions/safety/etc standards dictated by the regulatory environment, you also need to fund months to years of Q/A testing to ensure your physical widget can be reliably mass-produced. And all this has be done before you have anything to sell for revenue.

Respinning a hardware prototype is generally slow and expensive (i.e. can't just recompile), with degree of slowness/cost increasing as you tread further down your development path.