THis I tend to disagree with because people are notoriously bad at calculating risk vs reward. That "flash judgement" for DC's is almost always punitive for the benefit of the improvised action which results in players who simply never try improvised actions because they can see that there is no actual benefit to attempting them.
For example, say the PC has normally a 60% chance of succeeding a standard action - attack, skill check, whatever. Now, if you reduce that success chance to, say, 35% (say by raising the DC one "level" or +5 to the DC) but the results of a successful check are only 50% better than if I just did a normal action, then, there's no point. That's a suckers bet. You need to give me 100% better results for a -5 (or 25%) penalty to success, otherwise, there's no point.
But, very, very few people actually understand that. There's a reason that the -5/+10 feats are written the way they are. -5/+5 is totally not worth it. If I am significantly increasing my chances of failure (and going from 60% to 35% is almost doubling my chances of failure), then my reward needs to be even more than what I am risking. Otherwise, it's not worth it.
And, "common sense" and "flash judgements" are almost universally wrong.