That is clearly because the aim is to get money, not to slow the traffic down.
The traffic coud EASILY be slowed down, there are countless methods to do this on accident black spots for example. But they would rather hide so that they get to fine people. Stopping non resident is even better because they have to part with cash on the spot, or their cars. That is why foreigners get stopped much more often (or rather people that look foreign)
Pensioners, Spanish people and rich looking people with expensive cars get stopped much less often
Thats why i started this topic in the first place, to find out our rights on this. Isnt it funny that almost nobody knows and understands what their rights are? I wonder why the goverments dont teach the people their rights? Is it so that we can be exploited much easier?