Deadly biological ones are problematical. Because they can kill your folks as well. Too hard to control.

But chemical weapons really can kill as many people as nukes, and have the bonus of leaving infrastructure in place.

However by treaty, chemical weapons are not used by countries against each other. And making the powerful stuff is difficult. Less difficult than nukes, to be sure, but it isn't easy. Plus people are more serious about those treaties. For instance the USA voluntarily destroyed most of its stockpiles. We haven't done that with nuclear weapons.

Plus there is the whole Mutually Assured Destruction thing. People really don't want to use weapons of mass destruction against a similarly equipped enemy. For instance during WW II the Germans developed nerve gas, but did not use it for fear that the allies had it. Conversely the allies stockpiled chemical weapons but did not use them on the Germans. Somehow that comforts me.

But you're completely right. For non-countries to get or deploy them is difficult, and the threats we hear about are BS.

Cheers,
Ben