Currently most zaps are worth pennies, sometimes sub-penny, which probably doesn't make people think that much before zapping.

Yet people with a large following and adding value to the community (not necessarily directly with their posts, but e.g. building open-source software, creating music, art, writing quality articles, tutorials etc. and announcing their work on Nostr) can fetch decent donations. This is a new economy, based on micro-donations rewarding people's effort, which can be anything from the micro scale (such as a meme or a joke) to work that could be published via traditional channels, but whose author chooses the new way, which is more fluid, scalable, decentralized and free.

Personally I feel I'm more likely to reward quality contributions with zaps than I am with likes.

I guess the issue with voluntary donations is there will always be people who choose to consume content for free. But for what it's worth, while I've always embraced the BitTorrent way of life, I've been finding myself zapping for Nostr notes and stacker.news posts and comments with little resistance. The small amounts make it easy to swallow, especially knowing that people are also zapping me. I'm happy to zap because I can afford it, and I know that when I can afford more I'll zap more, and karma will do its job, because with this new financial system there is no friction in its way.