Speaking of good reasons for easy wins:
One thing I like is to throw easier challenges at PCs when they are engaging with mechanics for the first time. For example, the first time characters encounter an extended test in Star Trek Adventures, I want them to understand the procedure, not be at risk of failing, so it’s probably going to be a simple extended task to get the process down.
I’ve done this with starship combat, group skill checks, and mass combat in multiple systems. Part of my though process is that the characters know what they are doing in these instances, even if the players don’t, so I want them to get a feel for what they need to do in order to “get the win” under more adverse situations.
This also reminds me of minions from 4th edition D&D. They have a good chance to hit, and still do reasonable damage. They are still just as hard to hit as you would expect for their challenge. But once you actually hit them, they go down quick.
The 2d20 system has a similar mechanic, where minor characters may not have any stress, so if you do manage to hit them, they are defeated/dead/taken out, but they have stats that are comparable to other characters, they just don’t have a “stress buffer.”