Why no Parachute in passenger aircraft?

Parachutes would add weight to the aircraft. Also, the passengers on board would not know how to use a parachute even if they had one, or might not be able to. An event in a passenger aircraft that might need a parachute would be very rare anyway.

Some smaller aircraft have 'BRS' parachutes which parachute the whole aircraft to the ground.

Commercial airlines do not carry parachutes as there is unlikely to be a situation which would merit their use. The costs (not neccesarily meaning financial costs) would far outweight the benefits.