I built an app for myself that I’ve been considering rolling out as a product. It’s built around SMS because I will always look at a text message but app notifications are constant and easy to ignore. But the whole idea of the product is built around not being able to ignore the thing the app tracks for you. So far in a limited release the only thing I’ve learned is that my free tier needs to be quite limited and that it’s going to cost a few bucks per month per user to run it, so I need to charge more than that. But you’re effectively paying to be texted about something specific. It’s not because you don’t want to opt into push notifications - it’s because you’re literally paying for something to cut through the noise. Im not OP but if they’ve got something similar going on, that’s a good reason to use SMS.

That said your concern is incredibly valid and it’s why SMS needs to remain somewhat expensive. Could you imagine if SMS was as cheap as email? Holy shit the spam volume.