Summary ATITD is a massively multiplayer online manufacturing simulation. Players travel through a virtual world loosely based on Egypt, manufacture goods, trade, build buildings, and compete (or cooperate) to pass tests.
In ATITD a relative noob with little more than free university skills can usually cooperate with a veteran who has purchased every single skill from every school, and both players can benefit from the cooperation.
There are a few justifications for the difficulties of travel
With the really long tasks, you can set an alarm on your cellphone and wander off to do laundry, or watch TV. With the really short tasks, you can stay relatively engaged. With the intermediate ones, it is more of a 1980s-era "waiting for the computer" purgatory.
Some of these waiting-based tasks are forgiving. If you don't come back in time to do another weave on the loom, your character has wasted a little time that it could have been manufacturing. No big deal. Some are not forgiving. If you miss the window to add a late malt to a beer kettle, the batch is ruined, and you have wasted 20 minutes to an hour.
Contrast with Diablo 2 where you can use a town portal to retreat to a safe place (town) while you take care of some real-life issue, and later return to resume your battle.
Festivals are the biggest example. The more people you can get to do the festival at the same time, the more points everyone gets. The individuals who are unable to rearrange their real life to accomodate this aspect of the game are at a disadvantage.
Another example is mushroom hunting. Participation in the Test of Darkest Night requires that you log into the game for a 1-hour window that happens about 3 times per day. The hassle is compounded by the fact that some mushrooms have a localized habitat and thus you are forced to deal with the inconveniences of travel.
Other examples include grape growing, beetles, fishing, and (to a much smaller extent) livestock.
This means that certain aspects of the game are degraded for the "casual player". Casual players will never be able to compete with hardcore players, that's how you tell the difference between casual and hardcore. It just seems a little wrong, though, that certain aspects of the game are unavailable or degraded in quality if you have a job/social-life.