Why would you need this to be the case? In my mind (im not an expert) I just imagine schnorrs batching signatures into one tx on the chain. And then its done. Why would you need to add years after?
In Bitcoin today we can do things like make a conditional signature in a multi signature. With three parties, one can pre-sign a transaction and lock it until a future date, then hand it to the other parties who can sign it at their leisure when that time is elapsed. This would not be possible with schnorr unless you also had the expectation that all parties would be online when the lock time expires.
Yes, to get the space/validation improvements you can get from schnorr you need interaction. But it's perfectly possible to use it in the same way as ECDSA, it only adds options, it doesn't remove them. For some applications the requiremetn that the participants isn't a big deal and they can enjoy those benefits, otherwise they don't.