t uses a unitless measure called “story points”. Unfortunately these are arbitrarily assigned, and then managers attempt to discern “velocity” from them. The problem is that teams aren’t all that stable, and you need lots of data points.
Agile Is The New Waterfall

So why use them? Again, it’s the rigid application of the tool that brings the process down. Unless you have a sponsor and business that wants predictability — in that case you have selected the wrong tool for the job.