A couple of alternate reasons that some, if not many, faithful avoid suicide-as-a-ticket-to-life-with-Him:
1. Their faith is not strong enough to motivate permanent action against temporary worldly troubles. 2. Their faith dictates that one's final action being murderous in intention would not (assuredly, anyway) permit their soul time for contrition to merit essential absolution. 3. Fear of death outweighs consideration of any good or bad in this world.
All three of these points distill down to there being comfort in the assurance that the sun will rise tomorrow, at least. It hangs somewhat with the optimism of the original post, though I propose the primary reason being that anxieties associated with the uncertain, unknown, or unknowable are of utmost concern, consciously or otherwise. In other words, one's choice to continue living is probably in preservation of the knowable status quo, though it's a highly personal question with variation.