I can see why that'd make someone cross, but it seems in line with how localstorage works + how browsers define their "private browsing" features. On Chrome, for example, when in Incognito mode, you can't undo-close-tab a tab after closing it. Effectively, every tab you open in these "private browsing" modes will sooner-or-later "self-destruct", including all its cookies, localstorage, etc. (iOS?) Safari just chooses "sooner" rather than "later."

If your site relies on using localstorage during the lifecycle of an individual page, you can always replace it with an in-memory mock polyfill if you notice it's missing. There's probably an NPM package for that.