Wasps are beneficial in that they keep down the numbers of insects, etc. in quite a wide area around their nests. They also (accidentally) help with pollination of plants. Wasps are active from around April when they hatch, but people generally don't notice them until around August - when they suddenly start bothering people in their search for sweet /sugary food.
This is a function of their lifecycle. From around April the workers go out and gather small insects (greenfly, etc.) and carry them back to the nest to feed to the grubs. In return, the grubs exude a sticky sweet nectar which is the workers food. At the end of July the young queens leave the nest to set up for next year. No queens = no eggs = no grubs = no food for the workers.
You can see what's coming next... the workers start making a real nuisance as they roam around, desperately looking for an equivalent food - e.g. your ice cream, cola, etc. - and will sting you to get it..!
If you managed to wipe out all the wasps nests in an area early in spring, you'd have no problems that summer with getting stung by them. Then next year, your garden would be overrun by tons of insects - and then perhaps you'd be overrun with spiders instead?
Which would you prefer? ;-)