CLAs represent an important legal protection, and I would never accept a PR from a stranger, for something being developed in public, without one. They're the simplest way to prove that the contributor consented to licensing the code under the terms of the project license, and a CYA in case the contributed code is e.g. plagiarized from another party.

(I see that I have received two downvotes for this in mere minutes, but no replies. I genuinely don't understand the basis for objecting to what I have to say here, and could not possibly understand it without a counterargument. What I'm saying seems straightforward and obvious to me; I wouldn't say it otherwise.)