Do freelancers actually need time tracking, or is it mostly for client trust?

I’ve been building Timether, a privacy-first time tracker for freelancers and small teams, and one thing I keep thinking about is this:

A lot of people say time tracking is about productivity, but for freelancers and agencies, I feel like it’s often more about trust.

Not “I worked 8 hours today” trust.

More like:

• being able to explain where time went

• giving clients confidence without constant check-ins

• understanding which projects quietly eat up your week

• proving work happened without screenshots or surveillance

• knowing when fixed-price work is becoming unprofitable

I’m curious how others think about this.

If you freelance, run an agency, or manage client work:
Do you track time mainly for yourself, for your clients, for billing, or not at all?

And if you avoid time tracking, what makes it feel annoying or unnecessary?