The practical consequences of running an outdated eslint version are, for most projects, zero. The cost of upgrading is non zero. So upgrading only happens when there's a compelling reason to update like:
- A real security issue - things like the reDoS example cited are part of the crying wolf that causes people to treat security scanners less seriously
- A new feature (lint rule in eslint's case, or maybe new JS syntax support) is desired. The new upgrade can be deferred until that time
- You're doing updates _anyway_ and update eslint as part of that housekeeping.