It's not (just) a question of difficulty, but one of nuisance. A large part of the problem with a large fortress is the micromanagement required to keep it running at all smoothly. Introducing MORE micromanagement is not something that should be done casually.
Deciding which way a bridge raises is a significant tactical decision for a significant construction. There's not necessarily "one right way" to make a bridge - compare the difference between a drawbridge and a retracting bridge, for starters. If you have a drawbridge that blocks an entry corridor when raised, do you want to pull it up into the corridor, giving some room for murder holes? (Possibly with a short drawbridge to lock them into that corridor - possibly combined with water pumps.) Or at the corridor's mouth, so the attackers can't get out of sight of your outside crossbow towers? Which way that decision goes dictates a big difference in strategy.
Dwarves should, on the other hand, be smart enough to build ramps in a way that makes sense, and shift material around so that it connects reasonably smoothly as they build new things around those ramps. A ramp is supposed to connect Z-levels. Some indication of which way it works and doesn't - say, shading the "solid" side of the ramp darker / doing something to the "empty space" side of the ramp on the upper level - might be possible to keep it straightforward, but so long as the functionality of ramps themselves is made plainer, I don't see why players need to be involved in every niggling detail. It also would add a new layer of complication to the very feature people are already saying there's trouble learning. Do you honestly think making this change would eliminate the forum posts from people stuck on ramps? I think it more likely that accidentally building ramps the wrong way would cause at least as many problems, maybe more.
Dwarven autonomy is a large part of the game's charm, too. It makes sense to order the general things we want done, but, well, would you be terribly happy if you were told not just to connect this floor to that, but which way the low end of the ramp should face? I don't think even the most inbred dwarven noble is supposed to be THAT stupid.
Re: Untelligent - the reason I(and likely others, though I can't be sure) am arguing for ramps to pick directions intelligently is because others are arguing they shouldn't. Nothing more.
Perhaps a ramp with no proper supporting wall(existing or planned) could light up an error saying "Unsupported" or similar, when you're trying to place it. Whether you can place it anyway or not is a matter for further debate.
Re: digging ramps - being able to designate from both sides - and automatically designating the corresponding tile on the other Z-level - might help make the initial digging clear. More feedback on them could be nice, though, indeed.