It doesn't mean that zero people use it. Thousands or millions of people used Hangouts, Google Reader, Google Code, or Picasa - they'd have been considered big YC successes.
If big YC companies all got shut down if they failed to turn into another letter in the FAANG acronym, maybe people would become reluctant to use services from YC companies.
I still use some Google services, but I check out my data on a regular basis, I'm not buying a Fitbit, and I'm not subscribing to Stadia because I want those things to last longer than I think Google will keep them around.