"Why just look at Trek and Cannondale?"
Probably because anyone new to bicycling or touring is not comfortable building up a complete bicycle themselves. You do have to know what to buy. Front derailleur clamp size. BB width, 68 or 70. English or Italian threading. Stem clamp size 1" or 1.125". Stem bar clamp size, 26.0 or 25.4. 700 or 26" wheels. Complete wheels or build them yourself from hubs and spokes. Seatpost size, 27.2 or 31.6 or
?. Long, medium or short cage rear derailleur. Double or triple front derailleur. Whaat chain length. What length of cables. V brakes or cantilever. Do your brake levers match the brake style. No V brakes with STI unless you also get the Travel Agents adaptor thing. If bar ends then you need the adaptor with V brakes or the Dia Compe 287V levers.
Lots of decisions someone who is not already very experienced with bicycle mechanics would not have any way to answer. And if you buy the parts directly through a shop and have them install the parts, your cost is much, much more than a Trek 520 or Cannondale T800. And if you buy the parts cheap through mail order, eBay, etc. and pay a shop to install them, you are still much higher in cost.
If I had to buy a 700C wheeled loaded touring bike, I would definitely go with the Surly Long Haul Trucker. But I already have a 700C loaded touring bike. And my next loaded touring bike will have 26" mountain bike sized wheels. But the only mechanical work I do not do on my bikes is where frame tapping, facing is involved or if I do not have the tool and can't see the cost justification to buy it.