Most likely that getting WakeMate manufactured was a painful experience and he wants to avoid physical products now.

WakeMate had a disastrous launch where some of their USB chargers lit on fire. I think Gabriel doesn't want to deal with/feel he can help startups with these sort of problems that only come up when you're making a physical product.

Most likely he got burned with the "real" world.

Perhaps that the real business of WakeMate is the software they build, not the wristband.