Comment by simonw

I heard a great theory about this recently.

The hardest part of onboarding a new customer to Cloudflare is the bit where you need to switch over to having them manage DNS for you.

If you're under a DoS attack or similar, waiting for DNS changes to propagate is the last thing you want to have to care about!

Cloudflare's generous free tier is an amazing way of getting that funnel started: anyone who signs up for the free tier has already configured everything that matters, which means when they DO consider becoming a paying customer the friction in doing so is tiny.