What's the point of a credit agency if they can't get paid for making their reports?
But they also provide what's essentially a vanity service where they give you a more detailed breakdown of the information they have on you. They're also allowed to charge for that.
The issue is that under the GDPR, they're also required to provide all the information they have on you, for free.
Now this obviously conflicts with their nice side business, so they're trying to herd people towards the paid offering.
I don't think making the free GDPR export more prominent would threaten their core service. After all, businesses interested in your creditworthiness don't want to make too many complex decisions themselves, so they'll continue to rely on Schufa's stamp of approval instead of wading through the details of your financial history. (And how do they know you're not hiding something from them?)
In the case of landlords it is possible that they ask the potential tenant to hand in a report as a precondition to even make a contract offer. In that case the potential tenant would have to pay for their own data if it weren't for GDPR. The Schufa uses dark patterns to trick people into buying data they legally are entitled to get for free. If you get around their confusing UI (we recently did...) they send you that infamous 30 Euro report for free without much more ado.