No need to be harsh.
As an armchair CEO, my guess would be that when promoting a 8kg limit, people feel more obligated to pack less which translates to fuel savings. The legal limit that is advertised has little to no effect on the fuel loaded. The hand luggage due to not being weighted is translated to an rough estimate, per person on the load sheets which means that the weight is irrelevant in terms of load and balance calculations.
With not one bigger airline AFAIK constantly weighing passengers and/or hand luggage, saying that exceeding the limits has serious safety implications is a bit far-fetched.

What is more ridiculous, is that an alliance with only 13 airlines can't allign the baggage allowance between each other.