On the other hand, snakes eating all the rats would be good for children. Rats are reservoirs for many human diseases, but the think on the snakes!! is a common alibi for forcing your neighborg not to having shrubs, roses, grass, climbers, rocks, ponds and everything that would make your own garden look duller by comparison.
For most areas, it's aesthetic.
Here in the south-east, a short lawn will have no mosquitoes but a grassy area will have plenty (as in you'll get 20-30 bites in one evening outdoors), so that's a strong motivation.