Webmaster do it more for the backlink than for the traffic. However exchanging links with a high traffic site can sure get you a lot of hits, but then remember to exchange links on the homegpage for maximum exposure.
Sure, for more exposure you could request a link on the homepage. But what about the apparent catch here, would you give a Link Back on your Homepage or pay high for the space? I think the trend now is to generate Links effective enough to attract Search Engines Crawlers to your website. These links are more economical and could be showcased as the increased PageRank.
It add additional traffic but not that huge. Basically link exchange is a SEO process which help your site to increase back links that will improve your SERP. From that huge traffic will came to your site.
Link exchange don't increase traffic, u just get links pointing to ur site search engines like one way links, where in link exchange, u get reciprocal links.
It's true that link exchange does not effect your traffic. You can have thousands of backlinks, and not receive any traffic
Of course, Link exchanging is a SEO process to gain traffic to our site. Traffic in the sense "The unique visitor to our site".