Retroospect on a basic usage takes like 15 seconds to fill weekly and only tracks 5 basic data points, allows anonymity and produces charts, breakdown reports, etc... it's a more lightweight product, demands less from users and cost less - quite different kettle of fish.

In my experience teams tend to stop using products that demand too much after little time unless you enforce their use, although these tools are probably a better choice if you want in depth reports.