Groundhand.....
The key driving force is lowest possible cost.
In doing that you define the level of ability and expertise deployed to the various roles.
I feel you have missed how this really impacts.
The wage paid, the money/time spent on training, the money spent on equipment (buying & maintaining) etc. and the company owners (board etc) requirements for returns on investment are what decide if you can do the job.
With the key drivers these days being the minimum cost while producing a profit (often miniscule in general business terms) there are few options.
If you could attract staff with suitable skills/abilities and trained them well they could of course operate as you suggest.
But given the current market place you will not get those people generally and will get neither the funds nor the time to train up beyond absolute minimums those you do get.
I'd go so far as to suggest that if you look closely at most HA's training units/plans (and I've audited quite a few in my time) you'll see that their primary purpose is actually to protect the company (HA) from the HSE in case of accident.
This means that your loading team leader/lead pax agent/load control agent or whatever etc. actually don't have either the knowledge or probably the ability to function in that way.
They can only follow a "list" starting at item 1 and ending when the task is complete. They don't understand what each step actually does or how it integrates with the others on their list or someone elses.
Someone mentioned boarding pax while fuelling ... that's a good one and while the rules vary carrier to carrier if we're honest just how many of todays pax boarding agents, loading staff, or a/c fuellers or anyone else might actually know what the requirements are to do this?
And if they don't know either the needs or even if it's happening then how do they ensure that they don't without knowing compromise the requirements.
Other, of course, than simply saying "can't be done" !!
I see one particular handling agent lose bags off trailers regularly simply because they will not/can not (?) teach their staff how to stack them properly so they don't all come off at the first corner (of course they never use restraints as I've yet to see any on their trailers).
I've seen (and argued against) HA's fixing staff levels for a loading shift based on reducing the team numbers by one for a shift because "we did it with XX last week so keep dropping it by one crew until we hit problems!.
I often wonder from the comments I hear just how many pilots still think that the person on the headset talking to them is an engineer liney rather than realising it's simply one of the loading crew.
I've had myself to explain to a HA finance manager (who had just been recruited from outside the industry) why staff numbers fell in winter and rose in summer.
Believe me no accountant wants to have the staff employed before the revenue to pay their wages starts coming in the door......
We live in a world of minimums and that in reality means minimum costs/skills/abilities.
Not because the guys & gals doing the jobs (or even most of their managers for that matter) want it that way.
In the current economic climate this seems unlikely to change barring a serious accident being caused.