Quote Originally Posted by boiga
Another issue are that there is no standardization for helmets in the league. There are newer technologies that help protect against concussions, but they are bulkier and heavier than the most common helmets now. Peyton Manning wears one for his own protection and it makes him look like a spaceman.

http://www.colts.com/images/news_pho...13_jax_836.jpg

Many younger players don't like the feel of the better insulated helmets or they think it'll slow them down, so they won't wear them. They would increase the lifespan of your average player a good deal though.

Edit: Here's a link to the npr transcript talking about the need for new helmets in the NFL and MLB.
If you read the article, helmets won't solve anything.