Column A, Column B. Building a small explosive device isn't hard. Building a million is very difficult, doing it covertly virtually impossible without the resources of a nation-state.
The problem with biologics is the self-assembly and replication machinery comes for "free." So the numpties who might otherwise blow up a trash can [1] now have a real chance of taking out a million people.
[1] https://en.wikipedia.org/wiki/2016_New_York_and_New_Jersey_b...
I also would like to hope that people that are likely to do such things are probably:
A) don't know how to break even the most basic guardrails of models
B) already in glasswings project
To prove point B - Theranos existed.
“Many of the largest and most responsible providers in the industry already screen and record orders voluntarily,” but there is no requirement to do so [1].