They could afford to give away the openers if they could win that revenue stream.
And Amazon would dump them in a second if consumers could instead click "Link your Home Assistant for secure deliveries and get $0.30 digital credit". Or more likely, Amazon would throw directly wired Dash buttons at consumers to enable secure deliveries.
I don't know what Chamberlain has to gain by sticking it to that particular demo. For HA to be a threat to the "partnerships" like Amazon, it would have to have an audience sizeable enough that Amazon would consider incentivizing adoption.
I would say it seems dumb to piss off the most passionate fans of home automation when you're a vendor of equipment that such people might want to buy, but Chamberlain has such a stranglehold on the market that I think they figure that even if they royally piss off that 5% of the garage door opener market, those suckers (or their garage door installers) will be forced to buy the gear from them anyway.