I actually worked at Ember for a bit before leaving when they get bought by Silicon Labs. The reason, internally, really was the fear that there would be a flood of low quality products that would make ZigBee look bad.

For that, you need certification, not gatekeeping.

Publish a set of tests a device must pass, broadly, to be certified compliant.

Allow manufacturers test their devices, for a fee, and win a certificate, or know where they failed. Much like you can take a language exam (say, TOEFL).

> fear that there would be a flood of low quality products

That's mental gymnastics. The fear is having to compete against cheaper products (possibly low quality, but possibly not). Even broken DRM is an excellent anti-competitive tool because no one can legally sell a competing product.

as opposed to ZigBee making ZigBee look bad as it stands now. Only big names looking for a lockin pick ZigBee.