The sibling comments make some of the same arguments, but here’s an article which also addresses it:
"An aircraft is most vulnerable during take-off and landing because it is closer to the ground (its biggest obstacle), and is travelling at low speeds and therefore is harder to manoeuvre. According to statistics from Boeing, almost three-quarters of deaths from plane crashes between 2005 and 2014 occurred during these phases of flight. But this is the time when a detachable cabin would least likely be successful at saving lives. Being closer to the ground would give the pilot much less opportunity to jettison the cabin following an incident and if it were detached it could well land in a built-up area."
To add to another comment larger planes have much better redundancy (multiple engines, multiple control lines, multiple pilots, etc.) so the situations where a parachute would help are much much fewer. So weight is probably better spent on making the redundant systems even more redundant than anything else.
The drastically higher speeds involved (250-300 knots airspeed, as opposed to more like 50-90 knots for GA aircraft), combined with drastically higher weights (think about the chutes needed for something like Apollo, which is nowhere near the size of a large passenger aircraft, and realize you need way more) would both be major issues. There’s also the simple fact that larger passenger aircraft tend not to fail this way, making it less likely such a system would help even if it existed.
I would expect the problem to be "mass goes up with size cubed, while parachute drag only goes up with size squared". I.e. you need a disproportionately larger chute (or more of them) for large aircraft. Those are dead weight in normal operation, which really hurts the economics.
I'll add on to the good points other have made here - smaller planes tend to fly out of small airports in the suburbs or the countryside. Larger planes fly out of much more urban areas, where there are a lot more obstacles, making a safe landing less probable.
"An aircraft is most vulnerable during take-off and landing because it is closer to the ground (its biggest obstacle), and is travelling at low speeds and therefore is harder to manoeuvre. According to statistics from Boeing, almost three-quarters of deaths from plane crashes between 2005 and 2014 occurred during these phases of flight. But this is the time when a detachable cabin would least likely be successful at saving lives. Being closer to the ground would give the pilot much less opportunity to jettison the cabin following an incident and if it were detached it could well land in a built-up area."
https://theconversation.com/why-a-detachable-cabin-probably-...