EDIT : This answer doesn't answer OP's request for the reasons why... However, some people looking for an answer such as the one asked by OP already knows the rules, and agree with it only when there is a critical risk of death.
When you see that slide deploying, just assume one simple principle, even if you don't smell any fuel fume nor see any flame or smoke. Slides aren't deployed for fun. They are deployed because the situation is so critical that the evacuation cost is probably less than any other of the remaining outcome (injured people, deaths ?)
Rules are there for a reason !
There's only one thing that can put an end to the internet bashing over people (if that's the problem) who bring their stuff with them.
Because you can't educate 7 trillion different people the same way (>80% doesn't listen carefully to emergency guidelines) and make all of them suddenly understand their 20,000
$ camera is not worth risking one single live (prepare to be sued and you'll spend at least 100,000
$ if one died - simple math)
Cabin luggage :
- less than 4Kg (8lbs)
- under 0.40m x 0.20m x 0.30m (100in x 50in x 76in)
- without any sharp component
- and with a safe and strong handle.
Then, no problem, everyone can bring his stuff with him upon evac. Simple rule, no possible sueing. You have your (critical) medication, your passport, business documents, credit card or cash, etc.
This answer doesn't really addresses the asked question; however, the asked question is an open and endless debate (pros and con) and have precise answer from the airline industry (NO ! There is no possible compromise when it comes to safety concerns), while mitigated answers from passengers point of view.
As long as you're not in the industry, never experienced a fullpanic emergency situation and lucky enough to get out alive or unharmed, you can't measure the importance of safety rules. That happens everyday : you can repeat passing that red stop until the day you have an accident. In similar cases, the only thing that works in a certain extent is strengthening the rules by removing the problem at the source, instead of trying to fix a design flaw at a later stage : disallows those large luggages in cabin ! Not the most seducing solution, but working (if correctly applied)
Side note : I may blame the crew for their severity, but I won't because I understand. I may blame some passengers with their huge bags (putting those behind at rish because that plane full of fuel CAN explode) but I won't because I understand, they are in panic, or not knowing the rules and aren't aware of anything else than themselves (my point is everyone has his own limit when put in extreme situations - you can't expect from everyone to get 100% prepared for the 987 possible scenarios on each flight while thinking of others)
I'm just both happy noone were injured on this case - EDIT: Wrong ! there were injuries -, and sad the practice has taken a so wide and careless proportion. If that continues, statistically, one big bad thing will happen sometime in the future, for sure.