They did. Windgap[1] took venture capital, took state funding from Massachusetts back in 2012, and didn't ship the product. Cool web site, though. Sanofi tried, but their product misfired at least 26 times and was recalled.[2] Teva tried, and their product was rejected by the FDA because of problems; they're going to try again with a new model in 2017.[3]
The companies that tried to enter the business were drug companies, not device companies. No expertise in volume manufacturing of medical-grade injection-molded plastic devices. There are companies which can do that.[1] There are automatic inspection technologies which can detect even minor flaws.[2] But the typical injection molding vendor isn't that good.
Consider the typical failure rate of ball-point pens. That's consumer-grade injection molding.
[1] http://www.windgapmedical.com/ [2] https://www.auvi-q.com/ [3] http://www.fiercepharma.com/sales-and-marketing/fda-swats-do...