any science to this as we all know a moth can fly around inside your house for at least 12hours
loads of insects etc can live without grass as well seems most of them have very little use for grass, they aren't cows
Insects can fly around your house for a few hours, until they tend to die often without the chance to breed
The grass provides space for the really tiny insects which may feed on it, then the larger ones feed on them, and your average "lawn" isn't just one strain of grass but multiple different species* and usually a variety of wild flowers as even the best kept lawn will usually have things like daisies and buttercups growing in it, and more around the edges.
A lot of insects as I understand it don't really have the homing instinct of say a bee so tend to go where the wind takes them, or from one plant/food source to another if you've basically got a barren area (fake grass, concrete) over a certain size they tend not to make the same crossings that they would if it was grass, or even better wild.
It's one of the reasons there has been a huge push for farmers to leave pockets of "wild" area, or things like hedgerows at the borders to their fields, as even a crop field doesn't exactly encourage a lot of the natural insects and other wildlife, but ironically does attract pest animals/insects** the same.
*I had to look for grass seed the other week and bought from a specialist supplier (far cheaper and fresher than the stuff you tend to get in hoimebase), and the variety of mixes is quite large even without looking for anything too specialised (most "grass seed" mixes have at least two or three varieties).
**Apparently if you plant a mixed field of complimentary crops you can significantly reduce the number of pesticides and weed killers you need as it turns out a bit of a mix results in less initial attraction for the primary pest insects, and helps reduce the spread.