Labwork with as loosely defined goals as life ("reproduce", "accelerate rise of entropy") is costly. It's a robust, deep objective long-term, but extremely inarticulate with poor ROI short-term.

A species of spider nailing down how to live on a particular type of rock on a particular island, in a very particular environment over millions of years, is simply not articulate enough "lab work".

Which is of course not an argument for killing off species. But it's an argument against approaching that moral question from such utilitarian perspective. You might easily end up with results you don't like, once you do the cost/benefit analysis in a less hand-wavy manner.