The collars disconnect with a sharp tug, similar to a cat jerking away.
You must have some special collars then as the ones sold in places like PetSmart, Petco, PetSupermarket, Wal*Mart et al take a horrific "sharp tug" or violent twist similar to what a medium size dog could do, or 25 lbs or more to release. My cats are no more than 12 to 13 lbs each. Far too light to make the collars-disconnect. Twisting them and jerking them doesn't make them disconnect. A straight pull of 20 to 25 lbs or more will. If you somehow somewhere found those that let go when a 13 lb cat gets hung, and feel they're safe, by all means use them.
And if you put them on correctly, they are not snug about the neck. From what I understand, the readers for chips are not as common as you make out, particularly in understaffed, underfunded municipal animal shelters, aka. dog pounds.
This is true. The stores all need to teach the cat owners how to correctly put them on the cats. So far the stores are not doing this. There are surely small poorly funded shelters in backwater areas that don't have chip readers. But there is no guarantee cats wont slip any collar before being found. There is no 100% guarantee any cat will be returned to it's owner no matter what we do. But we do hear increasingly of cats being reunited with their owns due to chips all the time. Some after as long as 9 years. How many because it had a collar and tag?