Airlines are finding it very difficult to retain check-in staff. It doesn't pay very much and is quite stressful. By the way you've ripped into me for trying to explain where improvements need to be made, you've provided a very good example of why people don't stay in the job. Would you stay in job where you are being abused and spat at (literally) for £980 a month?
Baggage allowances should be printed on your ticket or e-ticket. Airlines will have these rules on their website. I can understand turning up with a case that weighs 26kgs when the limit is 23kgs. An agent can work around that. It is the people that turn up with 3 bags at 40kgs and create a scene when they are challenged. My initial point is that these are the people that hold up the lines.
As I said, it is the "management" of these issues that will make the difference. Personally, I would like airlines to be more pro-active in ensuring passengers are advised of the baggage allowances during the booking process however from my experience it is the passengers that are fully aware of their allowances but will approach the check-in desk in defiance that are the cause of some of the congestion.