It depends on how the data is used and if an easy delete option exists. There is a valid use case for working around browser behaviour not user behaviour:

> browsers will unceremoniously delete IndexedDB, LocalStorage, and/or SessionStorage without warning under storage pressure

If you have an app that stores a small amount of data client-side (preferences, data to allow operation while unable to connect) but is not used very often it's stored state could be evicted because of a few large apps because the browser drops data on a "last used" basis because it has no way of knowing that this bit of data might be more important than the data touched more recently. The user might not want a small amount of practical data for an app that they used on their morning commute being evicted because they've touched some large games over the weekend. For a large device this isn't going to be an issue as you are unlikely to be that limited for space, but for a cheap phone with limited storage it could be a real inconvenience.

Any app doing this should have a very easy and obvious "purge my data from this device" option, to maintain the user control. In fact to do it properly right, the local storage should be opt-in ("Do you want to keep some data locally to speed up this app and allow it to be used offline? Yes / Not now / No and don't bother be again") with the app continuing to function without the local data cache.

> I'm going to continue to track you even after

Of course it will get used for this, it would be naive to think otherwise, it is after all essentially a structured evercookie, but that doesn't stop the idea having good uses too. The existence of arsonists doesn't mean you need to ban all uses of fire.