Why would a startup do that? Hardware is low-margin difficult, capital intensive, long sales cycles, long rampups until revenue, volume sales are very trust-based (hard to get in when not established), expensive recalls, product compliance, etc. In addition the trend for the last 30 years of electronics is integration, completely opposite of modularization. I am very pro open source hardware and software (and contribute to both) - but I find it completely understandable that there are few startups/companies in this space.