Immediate and public disclosure is the only responsible disclosure there is and I commend (and monetarily contribute to) the OpenBSD Project for their soft stance against embargoes.
Operating in opposition to that, a large portion of the security industry plays along for reasons varying from personal pride (appealing to authority makes you feel like one of the good guys) to the extremely lucrative payouts for selling 0day to nation states. It's no surprise that the higher your profile in the industry and on twitter, the easier time you have getting paid out on bug bounties. All of this hurts users.
I develop and maintain software and software infrastructure for a living. If you find a vulnerability in work I am responsible for, please rake me over the coals as publicly and loudly as you can. That motivates the PTB who fund my work to resolve the issue better than anything else.