A machine I can actually use, portability. I have enough servers, adding nginx and certbot to one isn't hard. Adding instances and load balancing isn't either should it be warranted. The "serverless" approach is the new one and thus the one that should seek justification.
> I have enough servers, adding nginx and certbot to one isn't hard.
I think this is key. If you have resources that are already serving things, the marginal cost of serving something else is low.
For a typical person not running servers for personal services, the upfront cost does not seem justified, when its so easy (and cheap) to setup and use the alternatives.