Probably most relevant for workspaces started through an app or webhook:
Restrict the number of runs. I.e. if it's been triggered more than x times in y amount of time, or if there are more than x non-unique triggers, don't run the workspace.
The main reason: one of the Flow's we're managing was recently hit by a DDOS attack, within the space of a few hours one particular workspace app was triggered about 4500 times. The workspace failed right away every time due to bad input, but it still took 1-2 seconds to do so, so that did eat up a big chunk of the capacity during those hours.
Another reason would be to prevent a user from re-submitting a job if it's taking too long. They might think something is wrong so they try again, and again, and again.