It wasn't a big problem in the days before manufacturers had the technical capability to prevent tinkering so why would you expect it to be a big problem now?
Because much more is in software than it used to be.
In the past, most of the key aspects of the radio were pretty fixed in the hardware. Whereas now, more and more of the radio is in software (and/or FPGA), or at least configurable from software. Tinkering in that case requires a "per person" level of skill. Whereas tinkering with software requires one person to be able to tinker, and then lots of people can use the result.
