I don't know about where you are, but here it is illegal to have affiliate content / paid promotional content and not explicitly state that it is affiliate content that you will benefit from. I'm typically pretty happy to sign up using people's referral links if I trust what they have to say, and see they've put in the work to promote it - but I always immediately just exit out if I see they've tried to hide a referral code.

The content they're promoting might be fine, but deliberately trying to mislead people isn't acceptable in any circumstance and it makes me lose faith in them & the content they're promoting.