There are numerous ways cancelling shows and removing them from the platform saves streaming services money, including not having to pay residuals and the ability to write off production costs as a loss on taxes. And, like others have pointed out, streaming services are historically driven by subscription fees instead of ads, and many viewers tend to binge watch shows rather than watch nightly throughout a full season. So all combined, the profit motive tends to push services toward many new short series suitable for binge watching that will keep people subscribed, but that can be quickly cut and taken as a loss.

This Marketplace article provides some other reasons, too.