Please do take note that I'm not saying anything like what you claim I said. I'm asking if it's something people commonly get hit by, as I myself haven't had severe issues with it.
I'm not saying others are misinformed or cargo-culting anything, just that I'm seeing lots of people who probably never get hit by DDoS in the first place (couple of visitors per day) adding CloudFlare by default as that's what they see everyone else is doing.
Of course if you do frequently get hit by DDoS attacks, there is nothing wrong with trying to protect yourself against it...
FWIW Cloudflare offers lots of useful services beyond DDoS protection—that's just one of them. Once you use Cloudflare for one service, it's nice to have all of your domains going through their DNS at the very least even if you were to bypass their stack.
Aside from ideological preferences or a preference for some other service, I don't see what you gain by avoiding them.