According to some reports on the forum, this setting is toggled on for new users:

I’m pretty sure most would prefer to track how many times they’ve watched something. It sort of defeats the purpose of Trakt as a tracking platform for everything you watch. New users who aren’t eager enough to search through settings might become frustrated with Trakt very quickly.
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In Review
Feature Request
9 days ago

CanePlayz
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In Review
Feature Request
9 days ago

CanePlayz
Get notified by email when there are changes.