With credit cards, the merchant is typically not liable for fraud provided they follow their processor's rules (such as chip cards inserted vs swiped). That's because the processing network has responsibility for checking the validity and either authorizing or denying the charge.

With paper checks, if the merchant is not using some sort of verification service, they're SOL if the check turns out to be fraudulent.

As to your experiences with companies accepting checks - they may be using check verification systems if they're getting enough checks to justify it, or they're in a place or in a type of business where there's a lot less check fraud. Criminals are much more likely to go write a rubber check for a $1500 bicycle they can quickly sell than they are to go write rubber checks for icecream or woodworking supplies.