An increase in birthrate in each winners country has been shown to occur roughly 9months after the world cup (i.e. 9 months after we won it there was an increase in the number of babies born, nine months after brazil win it there's an increase, etc). I imagine it also follows on a city level with premiership/FA Cup, Champions league wins, etc.
Watching our team win makes us happy, which makes us more pleasant to be around, better relations with family and friends. Losses can work the other way, even in minor ways.
We want to believe it's not important, and really it isn't important, but that doesn't mean wins and losses don't affect us.
