Think of zaps as value 4 value likes. Traditional social media reactions are fiat mindset and valueless.

Having them public allows people that follow you to see what you value so they might find people to follow. Clients might not work this way yet, but I think they will.

I'm a non-custodial advocate, but throwing some change into a Wallet of Satoshi and just using that as a zap wallet, while keeping your Zeus for your real spending on your own node. Perfectly fine to me.

The future nostr clients will include zap wallets.