I have seen exactly zero people calling for the age of consent to be raised. I have also seen exactly no calls for banning of pornography outside of the extreme religious conservative sphere.
There has been discussion even in secular settings about raising the minimum age for sex/porn workers to 21. The secular reasoning is to help prevent exploitation with the idea that some of the 18 year old performers don't understand when they're being taken advantage of, or the full repercussions of their actions. I think August Ames suicide kick off some of this discussion.
I think an enormous percentage of people in their early and mid 20s are largely clueless about predatory business practices and how they can be impacted by them. Everyone is different, but I personally may have been more vulnerable to shady business people when I was 21 than when I was 18; I was still clueless but felt more like an adult and was less likely to seek the wisdom of my parents for certain decisions. Each case is unique, but I don not think this situation is similar to an age of consent for the consumption of alcohol, tobacco, etc.
> I think an enormous percentage of people in their early and mid 20s are largely clueless about predatory business practices and how they can be impacted
And yet the same stereotype is said for elderly people being susceptible to scams, etc. Jokes about limiting granny porn aside, it's still generally viewed as a preposterous thing to suggest for elderly people to limit what they can do based on age.
As you pointed out, wisdom about X/Y doesn't come with age, it comes with experience, and there's many variables to determine what you get to exposed to when and what one's needs/desires are.
In this case we're not talking about age of consent for sexual activity, but instead for a business activity. The financial lure may be even stronger for a 21 year old since people at that age may have more financial responsibilities and can still just as easily get duped into a decision that they'll regret for many years to come.
I am simply concerned that such a rule as you're proposing would have virtually no impact on improving this situation. Furthermore, it may push some young adults into an illegal world of sex work where they do not feel as though they enjoy the protections of the legal authorities if they are exploited or even trafficked. I'm not saying that you're definitely wrong, but I am just concerned that your proposal would have a very limited positive impact. These are just my thoughts which could be totally wrong.