Precisely why I won't be doing it - I'm not committed to the cause.
1) I'm not convinced global warming is happening
2) If it is, is it natural or man-made?
3) Regardless of the answer to 2, can we do anything to stop it?
4)... without making it worse because we don't know what we're doing?
Certain things make sense to do, regardless of my 1 - 4 above, like cutting down on non-biodegradable waste, etc. But many don't, and some may well make it worse (like apparently the mass planting of trees, to prevent global warming, leads to massive erosion)
Anyway, this isn't the right thread to debate these issues, but I wanted to point out that some of us aren't not doing it just because we're lazy, but because we're also making a point (just one that's opposite to the point you're making).