Why are some pills almost exclusively in blister packs and some not?

Question

I’ve noticed some medications in pill form are almost always in blister packs (e.g. Allergy medication) or somehow otherwise individually sealed. Others, like Tylenol, are often sold “loose” in a bottle where they are not individually sealed. But then if you get Tylenol Cold & Sinus, it will be invidiually sealed.
Why can some of these meds be “loose” and others seem to require individual packages?

In:

Answer 1

[US] If my memory serves, pseudoephedrine, a decongestant which can only be sold behind-the-counter at pharmacies, is typically required to be sold in unit-dose packaging like blister packs (and therefore any combination which includes it).

There was also a push to sell loperamide (Imodium) in blister packs to try to discourage abuse.