Agreed that it's not a necessity. I've never used it and I've brewed up to 13% beers.
"More yeast" is a relative term. As in one package or vial? Probably, yes. Most beers will benefit from more yeast, to a point. Many of us use starters for that purpose, as it allows us to jump start the yeast and also create more of them...which will result in a better, faster and more complete fermentation. I have gotten in the habit of always using a starter, a 1L for 5 gallons and around 1.5-2L for ten gallons. For really big beers, in the 10%+ range, sometimes I'll do a stepped starter (essentially doubling the yeast)...but my testing has showed that process to not provide as much benefit as a basic starter.
You can also use multiple packs of yeast, but if you're using the premium stuff, that can get expensive at 6-7 bucks per pack. That's why many of us do starters as well.