On the contrary: If Project Zero finds a 0-day in a product I know I use, and I know that product is Internet Facing, I can immediately take action and firewall it off. It isn't always the case that they find things like this, but an early warning signal can be really beneficial.
For customers, it also gives them leverage to contact vendors and ask politely for news on the patch.
Maybe I don't understand the threat model here: what kind of public-facing services are you running that are simultaneously (1) not already access-limited, and (2) not load-bearing such that they need to be public-facing?
(And to be clear: I see the benefit here. But I'm talking principally about open source projects, not the vendors you're presumably paying.)
Some companies might be willing to compromise functionality to avoid compromise of their networks.
There's always a usability / functionality vs security tradeoff
Unfortunately I think most of the products you use have 0-days in them, it's just that Project Zero hasn't found them yet.
Unless the 0day is in your firewall.
Fortinet strikes again...