Why are they not until the customer is comfortable with the platform and willing to convert. Once they have been sufficiently educated and understand the value of the offering.
Who decided a weeks based trial system was the right idea.
Was this set in by payment gateway providers like stripe?
You want people to explore the value, but not start using too much of it for free. And you also don’t want to be to loose so they forget about actually trying.
There was a recent article here where they described how they realized that two weeks was way too short for their customers to sufficiently test it (some sort of developer/ backend tool).
On the other hand, more consumer oriented apps will benefit from shorter periods because it drives quick engagement and consumers are quick to jump on another shiny thing.
A lot of companies do Freemium versions or Reverse Trials where usage counts down based on user activity instead of time for the reason you're describing. But it's way harder to get people to upgrade from Free than to get them to convert when a time-based trial ends, generally.
Just like with WinZip and WinRAR - do you remember how that used to count up the days when you opened it? It wasn't uncommon too see people who were thousands of days into their "30 day" trial.