Because I view capitalism (or, strictly speaking, capital) as authoritarian (mandating human energy be expended to its ends, working in tandem with welfare states towards administered living), exploitative (the labour produced by wage labourers in aggregate is less than the aggregate profit created due to their labour) and allowing only an ever-shrinking space for genuine human expression (it degrades art by forcing it to be marketable and commodified).

I'm not alone in this; even pro-capitalists agree that a relationship can be exploitative even if both parties benefit in some way - they just disagree that capitalism is the cause of such a relationship which we can see the world over.

I think the argument for capitalism improving peoples' lives by measurable degree is a valid one, but it is only as valid as the argument that feudalism (for instance) improved the lives of those without any sustenance or access to land at all. I think we have the capability to do better than pursuit of profit.

I never said it wasn't. But like all things there are multiple aspects, not merely 'pros' and 'cons'.