Cloudflare is 'dominating' because of their free tier. There are other services actual companies use. Fastly, Akamai, AWS Cloudfront, CacheFly and more.
CF having that free tier is a HUGE reason me and people I know stick with it. None of us want to have to throw money at a CF-like service for a low-traffic site, or for an MVP, or... At some point, it definitely becomes worth it, but Cloudflare's free tier is a HUGE boon early on imho.