27% of the UK adult population have a criminal record, mostly for minor misdemeanours.That's a lot of people to exclude from things.
You say that, but why - as someone who has managed to get through six decades of life without one - not have an advantage ?
The whole point of having a criminal justice system is that the penalties deter people. If society chooses to ignore them, then maybe society shouldn't be surprised that people aren't deterred.
Speeding in particular is treated like a joke. And despite all the pathetic reasons people (who, mysteriously all tend to have convictions) dream up, there really is no excuse.
(For full disclosure I attended a SAC for 35 in a 40 when I was adjusting my speed limiter down. One of the best 4 hours in my life - learned a hell of a lot.)