The contract is signed for when bad things and disagreements happen, not for when everything is going good. In my opinion “I had no contract and everything was good” is not as good example as “we didn’t have a contract, had major disagreement, and everything still worked out” would be.

Even though I hate bureaucracy and admin work and I prefer to skip as much as reasonable to move faster, my default is to have a written agreement, especially if working with a given person/org for the first time. Generally, the weaker party should have the final say on forgoing a contract. This is especially true the more complex and difficult situation is (eg. living/travelling together, being in romantic relationships).

I agree with the general view that both signing and not signing have prons and cons and sometimes it's better to not sign and avoid the overhead.