All the above mentioned plus airlines shortening turn round times to get better utilisation of their expensive aircraft. Many airlines then still require all the services that were there on the original longer turn round times so all the different sections are jostling for position on the aircraft at the same time so that they can make sure that they don't get a delay attributed to them. January sales bargain hunters have nothing on these guys!
On many aircraft types the room between the catering high loader and the Lower Deck Loader when in position on the aircraft is very minimal, so if one is slightly mis positioned it creates a big problem for the other.
Aircraft design is another factor. I am a fan of Airbus but the idiot who thought of making the A319 with a containerised option should be shot! The clearance between a conventional high loader and the No. 2 engine when positioned on the forward hold is the proverbial cigarette paper. This encourages the driver to position at an angle and increases the possibility for damage. The company I work for had to invest in two smaller High Loaders for 2 flights a day because we had 2 incidents of damage in 6 months using the regular high loaders and the only sure way to prevent re-occurrence was to invest in expensive specialist equipment.
Airport design is another factor to be considered. Land is expensive so airports need as many stands in as small a space as possible. There are standards for stand sizes but the minimum sizes allowed are very cramped when all the services are squeezed into a short turn round time.
Hope this helps