Christian "purpose" and "meaning" in life.

[Esquilax]

The mouthpieces who claim to speak for their god don't actually pass on the message of how not to sin; they just tell us not to. These are not representative of any kind of moral framework, they're just pronouncements about certain types of behaviour. It's telling Dorothy not to look behind the curtain, rather than why she shouldn't or how she can avoid it.

Galatians 5:16-26
New International Version (NIV)
16 So I say, walk by the Spirit, and you will not gratify the desires of the flesh. 17 For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever[a] you want.

So... your response is just "you just do it!" And you can't see why this is a problem?

This is the problem with your religion: it makes you okay with answering "why?" questions with "what?" answers. It makes you alright with anything, so long as the correct space wizard commands it.