Most aircraft, B737 and smaller, are non-containerized, bags are hauled out to the gate and sent up a conveyor belt to the cargo hold door. Baggage is then pushed and stacked by one or two staff inside the hold. The space is not high enough to stand in, so most work gets done while kneeling. Bags will not get thrown very far, if at all, as it is ergonomically too difficult and physically exhausting, to do all the that twisting with over 100 bags per flight, many times per shift. However, bags sometimes fall off the conveyor belt, so that's a 6ft fall onto concrete. Anytime an employee touches a bag is an opportunity for mishandling/drop/fall/drag.
On larger flights, the bags are loaded and containerized within the terminal's baggage area and brought out to the gate for transfer in to the aircraft hold on a large elevating platform. Less likely to get bag damage on these aircraft as there is less human (mis)handling.
Theft is rarer these days with all the internal security cameras...essentially to monitor for baggage system blockages and backlogs. Zippered bags can still be easily opened and reclosed without your knowledge. Invest in a little TSA lock (some have a tamper pin that pops up when it has been opened by TSA (they will leave a note inside your bag saying they inspected it) or non-authorized master key holder.
Hardsided baggage is best. My all time favourite was the 29" Samsonite Oyster...the Timex of bags - took a licking and kept on ticking.
And...get a lashing strap to wrap around your bag to prevent accidental opening from dropping and getting hit by the automated kickers that redirect your bags down a myriad of belt systems.
Happy and safe travels everyone!