Why do most sites not follow heat maps?

I see Google has click through heat maps but most good sites put ads over to the right. Which is the best way?

 

Best for who?

Having the best click through isnt always what webmasters want. Sometimes you want to keep users on your site for a while before they click away, so they come back / tell other people about your site
Having the best placed add so that people click it isn't always such a great idea, it depends what you want from your site in the long run.

If I'm almost forced to click an add on a site,
I'm probably not likely to revisit it in the future

 

Exactly right. My adsense sites follow the heatmap pretty closely but my other sites are more content rich. With these sites there's a few ads along the side bar and maybe within the content but its more important that visitors hang around keeping my bounce rate low.

 

The adsense heat map gives a general view on placing the ads on your site. It need not be scrupulously followed and I have seen many people getting a decent ctr even with altered ad positions as against that advocated in heat map. That could be due to differences in the taste and preference of the individual visitors...

 

Find your own 'heat maps' is better than what Google suggested.