In Microbes I have difficulty settings that make the game almost impossible to lose. I think it's a good idea to do that.
I strongly disagree.
Many games present you with a task and a reward for completing this task. Snowman is such a game.
You are thrown in a hard level and you get a reward for completing this level, which is access to the next level, a congratulations screen at the end and a score you can compare against your friends and enemies.
Furthermore it presents you with mechanics you are supposed to learn and master. Managing your snow reserves is something you need to plan and master. Exploiting enemy patterns and combat is something you need to master.
In a way this is a dialogue, the creator of the game presents you with a challenge he created and you have to react to this, adapt to his obstacles and eventually overcome them. Learning and mastering new skills in the process, as well as building your own strategies and maybe even exploiting weak spots of the game.
This is what is fun to me at least, not the specific act of blasting away circle-like enemies with simplistic while balls of "snow", not jumping over an endless abyss over and over again.
All of the above is meaningless if you take away the challenge.
What is a reward worth if it's basically just presented to you on a gold platter? How are you supposed to achieve new skills and develop new strategies if the game is easy enough for any strategy to work? If a fail state is so hard to reach that you are basically free to do anything, how are those acts of "anything" meaningful in any way, how can those be "fun"?
Granted this is talking on a very high level about a rather simplistic platformer. I think it's true nonetheless, especially if you are shooting for a C4A score there are tons of possibilities to develop strategies in various levels (which snow not to collect, which enemies to kill, etc.).
Also granted removing the cost of jumping will not make the game trivial, yet it will change the very core mechanic and make some passages meaningless (even if that's just on one difficulty setting). I would still be interested to see how it would play out in particular, but I think the problem of the game being to hard can be tackled in another, non-intrusive way (by adjusting level individually, removing enemies, adding snow, etc.).
Finally, there are so many good games being released every day, every week, every month. There is no way you are going to complete them all and I think there is no need to.
Play a game until you feel like there is nothing left to "learn", play until you are not having "fun" any more (though the definition of "fun" might vary), or rather play until you are not "engaged" any more. This does not necessary involve completing the game, especially if there is no "story" or you don't care for it.
Completing Snowman just grants you with a C4A score (although you actually can submit it at any point), if you care for that you probably also care for mastering the mechanics (the game is possible to beat and there definitely is a skill- and learning-curve), if you don't, well then just don't try to complete it.