What they want to solve?
Radio is a shared medium and everybody has to follow the rules. Especially there are parts of the spectrum used by so-called first user like weather radar, military use, and alike. Originally radio was seen and considered as an somehow unlimited resource like IPv4 addresses. But then this this unlimited resource became very limited like IPv4 addresses. So now, we have many radio frequencies used twice by so-called secondary users. The secondary user can use the spectrum as long as the first user do not use it. This is e.g. in the 5G with Wifi.
This legislation is to (hopefully) assure that everybody plays by the rules. This realized by certifications. But the problematic nature of SDR is, that software controls the behavior and software can be replaced easily. For that reason none of those people, which govern the radio usage, like SDR. They want to lock down the device, so that they are sure that every body plays by the rules.
Anyone who can replace a baseband firmware can also build or acquire hardware that is capable of WiFi-range TX.