Killing Merchants?

I typically do not kill NPC’s in From games because you get their gear when you do their quest etc.

However the merchants drop a bell bearing containing their shop inventory when killed (from what I remember). I don’t know if this makes all merchants hostile either.

Do people typically end up killing the merchants to have easier access to shop inventory?

Are there any downsides? (Like I know the a hole in stormveil eventually gives an upgrade stone so it’s not worth killing him over some runes).

Looking for advice or your experience.