So far, I've only had about 3 phones in my entire life, and I can totally understand the need to have a backup phone.
I had never thought about having accounts that I couldn't recover in case I lost my phone, I only use the common apps (Whats, Telegram, and Google Authenticator) and I think those would be the most important in case I lost my current phone; but none of this is anything I can't recover with a backup or a few messages to support... although not too long ago something happened to me with Binance that so far has made me unable to use my account, lol. Not exactly the same thing, but I moved countries and totally forgot to change the phone I have 2FA linked to, and Binance is asking me for an absurd amount of documents to verify my identity.. something that is not worth it (at least not for now) because I don't even have cryptos in there xd.
After all, whether you can lose your phone or not, backing up your data will always be a good idea. After all, investing 50-100$ in a backup phone sounds more profitable than losing important data or accounts with money inside forever.