Why do wasps keep coming into our recently converted attic to die?

hard to say...with most attic conversions I see, they are not all that air tight and if there is central air condition involved that might be killing the wasps,, they would be finding a way in (not being all that air tight) and then the central air will be too harsh an environment for them to survive, dries insects out. If the attic had been treated in the past more than likely it would of been a dust formulations, possibly the wasps getting in are dieing from an old insecticide treatment, dusts don't break down as fast as other insecticide treatments. Lack of spiders would have nothing to do with them dieing, they don't eat spiders, but feed them to their larvae.